Custom theme support

[sgruendel]

• Add theme = "custom" support so Hunk can read theme colors from config.toml.
• Let custom themes inherit from any built-in base theme and override palette and syntax colors selectively.
• Normalize git diff --no-index patch prefixes so colorized pager and patch input still parse correctly.

[greptile-apps]

Greptile Summary

This PR adds theme = "custom" support to Hunk, letting users define a palette in config.toml that inherits from any built-in base theme and overrides colors selectively. It also normalizes git diff --no-index patch prefixes (1//2/ → a//b/) so the pager can parse those diffs correctly.

• Custom theme config (config.ts, types.ts): New CustomThemeConfig / CustomSyntaxColorsConfig types; validation for base IDs and #rrggbb hex colors; two-layer merge (global → repo config) with field-level syntax override merging.
• UI wiring (themes.ts, App.tsx, AppHost.tsx, appMenus.ts): buildCustomTheme inherits the full palette from a built-in base, availableThemes() appends the custom entry to the cycle/menu list, and resolveTheme dispatches to the custom builder when theme = "custom" and a config is present.
• No-index normalization (loaders.ts): normalizeGitNoIndexPrefixes rewrites the three header lines that differ between git diff --no-index and standard git diff output, applied before patch parsing.

Confidence Score: 4/5

Safe to merge; the custom theme feature is well-tested and the wiring through config resolution, bootstrap, and UI is consistent.

Two edge cases in the changed paths are worth watching: the greedy regex in normalizeGitNoIndexPrefixes can misparse diff --git headers for filenames that contain 2/ as a literal substring, and a user who sets theme=custom without a [custom_theme] block will silently get graphite with no diagnostic. Neither affects the happy path or existing functionality.

src/core/loaders.ts (regex robustness for --no-index paths) and src/core/config.ts (missing validation when theme=custom has no accompanying custom_theme section).

Important Files Changed

Filename	Overview
src/core/config.ts	Adds custom theme config parsing, validation, and two-layer merge. Logic is correct; silent fallback when theme=custom has no [custom_theme] section is a minor UX issue.
src/core/loaders.ts	Adds normalizeGitNoIndexPrefixes for --no-index patch header rewriting and threads customTheme into AppBootstrap. The greedy regex in the diff --git line can mismatch paths containing 2/.
src/ui/themes.ts	Introduces buildCustomTheme, availableThemes, and availableThemeIds; extends resolveTheme to handle custom. The inheritance and lazy syntax style construction look correct.
src/core/types.ts	Adds CustomThemeConfig and CustomSyntaxColorsConfig types; extends AppBootstrap with optional customTheme field.
src/ui/App.tsx	Switches from static THEMES array to availableThemes() for cycling and menus; passes customTheme into resolveTheme. themeOptions is correctly memoized.
src/ui/AppHost.tsx	Properly threads customTheme from resolveConfiguredCliInput into loadAppBootstrap for daemon-driven reloads.
src/ui/lib/appMenus.ts	Replaces static THEMES import with an availableThemes parameter, enabling the custom theme entry to appear in the menus.
src/core/startup.ts	Passes configured.customTheme into loadAppBootstrap; straightforward wiring change.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[config.toml: theme = custom] --> B[resolveConfiguredCliInput]
    B --> C[readCustomTheme global config]
    B --> D[readCustomTheme repo config]
    C --> E[mergeCustomTheme]
    D --> E
    E -->|CustomThemeConfig| F[loadAppBootstrap]
    F -->|AppBootstrap.customTheme| G[App.tsx]
    G --> H[resolveTheme themeId customTheme]
    H -->|theme=custom + config present| I[buildCustomTheme]
    I --> J[builtInThemeById base]
    J --> K[Merge palette overrides]
    K --> L[withLazySyntaxStyle merged syntax]
    L --> M[activeTheme]
    G --> N[availableThemes customTheme]
    N -->|append custom entry| O[themeOptions for cycle and menus]
    P[git diff --no-index patch] --> Q[normalizeGitNoIndexPrefixes]
    Q -->|1/ to a/ 2/ to b/| R[normalizePatchChangeset]
    R --> S[parsePatchFiles]

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Comments Outside Diff (2)

1. src/core/loaders.ts, line 452-455 (link)

   Greedy regex may misparse diff --git headers with unusual paths

   The first capture group in /^diff --git 1\/(.+) 2\/(.+)$/gm is greedy, so the regex engine finds the last occurrence of 2/ in the line as the boundary between the two paths. A filename that contains 2/ as a literal substring (e.g. tests/2/case 2/tests/2/case) would be split at the wrong 2/, producing an incorrect a/… / b/… pair and breaking the downstream patch parser. Switching the first group to a lazy quantifier ((.+?)) won't fully eliminate the ambiguity for such names either, but it does resolve the more common scenario where paths contain /2/ as a path component (e.g. feat/2.0/auth).

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: src/core/loaders.ts
   Line: 452-455
   
   Comment:
   **Greedy regex may misparse `diff --git` headers with unusual paths**
   
   The first capture group in `/^diff --git 1\/(.+) 2\/(.+)$/gm` is greedy, so the regex engine finds the *last* occurrence of ` 2/` in the line as the boundary between the two paths. A filename that contains ` 2/` as a literal substring (e.g. `tests/2/case 2/tests/2/case`) would be split at the wrong `2/`, producing an incorrect `a/…` / `b/…` pair and breaking the downstream patch parser. Switching the first group to a lazy quantifier (`(.+?)`) won't fully eliminate the ambiguity for such names either, but it does resolve the more common scenario where paths contain `/2/` as a path component (e.g. `feat/2.0/auth`).
   
   How can I resolve this? If you propose a fix, please make it concise.

2. src/core/config.ts, line 386-411 (link)

   theme = "custom" without a [custom_theme] section silently falls back to graphite

   When a user sets theme = "custom" in their config but omits the [custom_theme] table, readCustomTheme returns undefined, so resolvedCustomTheme stays undefined. In resolveTheme, the requested === "custom" && customTheme guard is false, no built-in theme matches "custom", and graphite is returned. The themeId state is therefore initialised to "graphite", silently discarding the user's intent with no warning. A validation check after config layers are merged — e.g., throwing or logging when resolvedOptions.theme === "custom" but resolvedCustomTheme is still undefined — would make the misconfiguration visible.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: src/core/config.ts
   Line: 386-411
   
   Comment:
   **`theme = "custom"` without a `[custom_theme]` section silently falls back to graphite**
   
   When a user sets `theme = "custom"` in their config but omits the `[custom_theme]` table, `readCustomTheme` returns `undefined`, so `resolvedCustomTheme` stays `undefined`. In `resolveTheme`, the `requested === "custom" && customTheme` guard is false, no built-in theme matches `"custom"`, and graphite is returned. The `themeId` state is therefore initialised to `"graphite"`, silently discarding the user's intent with no warning. A validation check after config layers are merged — e.g., throwing or logging when `resolvedOptions.theme === "custom"` but `resolvedCustomTheme` is still `undefined` — would make the misconfiguration visible.
   
   How can I resolve this? If you propose a fix, please make it concise.

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
src/core/loaders.ts:452-455
**Greedy regex may misparse `diff --git` headers with unusual paths**

The first capture group in `/^diff --git 1\/(.+) 2\/(.+)$/gm` is greedy, so the regex engine finds the *last* occurrence of ` 2/` in the line as the boundary between the two paths. A filename that contains ` 2/` as a literal substring (e.g. `tests/2/case 2/tests/2/case`) would be split at the wrong `2/`, producing an incorrect `a/…` / `b/…` pair and breaking the downstream patch parser. Switching the first group to a lazy quantifier (`(.+?)`) won't fully eliminate the ambiguity for such names either, but it does resolve the more common scenario where paths contain `/2/` as a path component (e.g. `feat/2.0/auth`).

### Issue 2 of 2
src/core/config.ts:386-411
**`theme = "custom"` without a `[custom_theme]` section silently falls back to graphite**

When a user sets `theme = "custom"` in their config but omits the `[custom_theme]` table, `readCustomTheme` returns `undefined`, so `resolvedCustomTheme` stays `undefined`. In `resolveTheme`, the `requested === "custom" && customTheme` guard is false, no built-in theme matches `"custom"`, and graphite is returned. The `themeId` state is therefore initialised to `"graphite"`, silently discarding the user's intent with no warning. A validation check after config layers are merged — e.g., throwing or logging when `resolvedOptions.theme === "custom"` but `resolvedCustomTheme` is still `undefined` — would make the misconfiguration visible.

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