feat(read,git): add read diet mode and smarter git diff filtering

[bz00qa]

Summary

Read Diet Mode

• rtk read --diet <file>: Markdown-aware filtering that strips verbose patterns while preserving essential content
  • Strips code block contents (replaces with "(code example omitted)")
  • Collapses tables (keeps header + separator, shows "(N rows omitted)")
  • Removes checklists (- [ ], - [x])
  • Strips HTML comments (single-line and multi-line)
  • Collapses consecutive blank lines
  • Strips decorative lines (===, ~~~)
• Useful for reading CLAUDE.md and other config files with reduced token overhead

Smarter Git Diff

• Auto stat-only for diffs >1000 lines — prevents token bloat on large changesets
• Binary file detection — shows "(binary file)" instead of raw binary content
• Context line stripping — only shows +/- changes, not surrounding unchanged lines (context is noise for LLMs)

Clippy Fixes

• Replace deprecated map_or(false, ...) with is_some_and(...) in git.rs
• Replace .last() with .next_back() in git.rs and container.rs

Changes

File	Description
src/read.rs	diet_markdown() + run_diet() + 7 tests
src/git.rs	Large diff auto-stat, binary detection, context stripping, clippy fixes + 3 tests
src/container.rs	Clippy next_back() fixes
src/main.rs	--diet flag on Read command + routing

Test plan

• All 897 tests pass (1 pre-existing binlog CRLF failure)
• 10 new tests (7 read diet + 3 git diff)
• cargo fmt --all --check passes
• Manual: rtk read --diet CLAUDE.md — verify reduced output
• Manual: rtk git diff on a repo with binary files

🤖 Generated with Claude Code

[pszymkowiak]

This PR has merge conflicts with develop. Please rebase:

git fetch upstream develop
git rebase upstream/develop
git push --force-with-lease

Labeling awaiting-changes until conflicts are resolved.

[CLAassistant]

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[aeppling]

Hey

We are cleaning up the codebase and improving the project structure for better onboarding. As part of this effort, PR #826 reorganizes src/ from a flat layout into subfolders.

No logic changes — only file moves and import path updates.

What you need to do

Rebase your branch on develop when receiving this comment:

git fetch origin && git rebase origin/develop

Git detects renames automatically. If you get import conflicts, update the paths:

use crate::git;        // now: use crate::cmds::git::git;
use crate::tracking;   // now: use crate::core::tracking;
use crate::config;     // now: use crate::core::config;
use crate::init;       // now: use crate::hooks::init;
use crate::gain;       // now: use crate::analytics::gain;

Need help rebasing? Tag @aeppling