Apply non-draft open PRs: parallelize @path resolution, fix TS casts, harden dir validation

[Copilot]

TLDR

Applies three non-draft open PRs into this branch. Core change: @path file stat resolution now runs concurrently via Promise.all instead of serially, with debug message ordering preserved. Two smaller correctness fixes round it out.

Dive Deeper

PR #93 — Parallelize @path stat resolution (atCommandProcessor.ts)

• Replaces sequential for...of + await over atPathCommandParts with Promise.all over mapped async handlers.
• Each path resolution collects its debug messages locally; they're flushed in original input order after Promise.all settles — preserving deterministic output.
• Introduces discriminated union AtPathResolutionResult (invalid | ignored | success | skipped) to make result handling explicit and type-safe.
• IgnoreReason renamed → FileIgnoreReason; ignoredByReason → ignoredPathsByReason for clarity.
• Measured ~3.5× speedup on multi-path queries (23 ms → 6.5 ms for 200 files across multiple workspace dirs).

PR #71 — Safer EventEmitter → Readable cast in shellExecutionService.test.ts

• as Readable → as unknown as Readable: the double-cast is the correct TypeScript pattern when the types have no structural overlap. Removes the stale // FIX comment.

PR #65 — Reject whitespace-only dir in memoryDiscovery.ts

• if (dir) → if (dir && dir.trim() !== ''): truthy whitespace strings (e.g. " ") would previously pass the guard and produce bogus resolved paths via path.resolve.

Reviewer Test Plan

1. Pass multiple @file references in a single query — confirm all resolve correctly and debug messages appear in input order.
2. Pass a whitespace-only string as dir to getGeminiMdFilePathsInternalForEachDir — confirm no path resolution is attempted.
3. Run shellExecutionService tests — confirm no TypeScript errors on the mock child process setup.

npx vitest run packages/cli/src/ui/hooks/atCommandProcessor.test.ts \
  packages/core/src/services/shellExecutionService.test.ts \
  packages/core/src/utils/memoryDiscovery.test.ts

Testing Matrix

	🍏	🪟	🐧
npm run	❓	❓	❓
npx	❓	❓	❓
Docker	❓	❓	❓
Podman	❓	-	-
Seatbelt	❓	-	-

Linked issues / bugs

Related to #93, #71, #65

[TrueAlpha-spiral]

IgnoreReason → FileIgnoreReason
ignoredByReason → ignoredPathsByReason

Cite_GPT:: PR #99 is the correct continuation path.
Do not merge #93 separately if #99 fully supersedes it.
Mark #99 ready only after confirming no hidden CI requirement is missing.

[TrueAlpha-spiral]

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