fix(hooks): prefer PATH gitnexus in stale hint

[sainiranjannallam]

Fixes #1938.

Summary

• Prefer gitnexus analyze in stale-index hints when a spawnable gitnexus launcher is on PATH, including Windows launcher suffixes.
• Preserve the existing npx gitnexus analyze fallback when no PATH launcher exists.
• Apply the behavior to the Claude hook, Claude plugin hook, and Antigravity hook adapter.

Validation

• npx vitest run test/integration/hooks-e2e.test.ts test/integration/antigravity-hook-e2e.test.ts
• npx tsc --noEmit
• npx --yes gitnexus detect-changes

[vercel]

@sainiranjannallam is attempting to deploy a commit to the NexusCore Team on Vercel.

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[magyargergo]

Summary

Reviewed with 7 lanes across 2 engines: GitNexus risk + test/CI, Compound Engineering (correctness, adversarial, maintainability, testing), and Codex (independent). Claude lanes share one engine; strong corroboration requires Codex + Claude agreement — here, Codex and multiple Claude lanes agree on Windows launcher policy drift.

Headline: This is a solid fix for #1938 — stale-index hints now prefer gitnexus analyze when a launcher is on PATH, with good e2e coverage and PATH isolation for the npx fallback. Before merge, align Windows launcher detection with the existing setup.ts policy (.cmd/.bat wrappers, not .ps1-only shims) and dedupe the plugin hook’s two PATH probes.

What looks good

• Pure-Node PATH scan avoids Windows which failures (#1938); Unix adds X_OK.
• Tests scrub ambient PATH (pathWithoutGitNexus) and add a synthetic launcher case — fixes flake when gitnexus is on the runner PATH.
• Covers CJS, plugin, and antigravity hook surfaces.
• Coordinator ran npx vitest run test/integration/hooks-e2e.test.ts test/integration/antigravity-hook-e2e.test.ts -t "gitnexus analyze" → 3/3 passed in the PR worktree.

Inline findings

1. P2 — .ps1-only installs treated as on-PATH (all three hook copies).
2. P2 — Plugin hook uses two different PATH probes for hint vs CLI spawn.

Lower priority / follow-ups

• P3: ~42 lines duplicated across gitnexus/hooks/claude/gitnexus-hook.cjs, gitnexus/hooks/antigravity/gitnexus-antigravity-hook.cjs, and gitnexus-claude-plugin/hooks/gitnexus-hook.js — extract shared helper (same pattern as hook-lock.cjs).
• P2 test gap: No e2e for PATH-on and stats.embeddings > 0 → expect `gitnexus analyze --embeddings` (hooks-e2e.test.ts ~96–129, antigravity-hook-e2e.test.ts ~132–161).
• P3: pathWithoutGitNexus() uses existsSync while hooks require isFile() + X_OK (hook-test-helpers.ts:48–57).

Refuted / not blocking

• GITNEXUS_HOOK_CLI_PATH hint mismatch: Pre-existing — stale hint was always npx gitnexus analyze before this PR; resolveCliPath() already handled augment separately (gitnexus/hooks/claude/gitnexus-hook.cjs:194–208). Optional follow-up, not a regression.
• UNC PATH hang: Theoretical enterprise edge case; statSync is wrapped in try/catch per candidate. Not reproduced; not a merge blocker.

CI / visibility

• gh pr checks shows only Vercel FAILURE (authorization required — unrelated to hooks).
• GitHub Actions status was not visible via the Checks API for this fork PR; treat CI green as unconfirmed from API evidence.

Hygiene

• Branch: fix/hook-path-analyze-command — one feature commit + merge-from-main (harmless).
• git diff --check and bidi control scan: clean.

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Automated multi-tool digest (pr-tri-review). Verify findings before acting.

[magyargergo]

P2 [code-read] — .ps1 is treated as a positive PATH hit, but setup.ts resolveGitnexusBin() explicitly rejects .ps1-only installs and falls back to npx (setup.test.ts:302). On Windows npm-11 layouts with only gitnexus.ps1, this hint says `gitnexus analyze` while MCP setup still uses npx.

Fix: On win32, accept .cmd|.bat|.exe only (mirror setup.ts:69); drop .ps1 from positive detection. Same block is copy-pasted at gitnexus-antigravity-hook.cjs:222 and gitnexus-claude-plugin/hooks/gitnexus-hook.js:200.

[magyargergo]

P2 [code-read] — This file now has two PATH strategies: buildAnalyzeCommand uses the new fs PATH walk (L188–227), while runGitNexusCli still uses where/which + hardcoded gitnexus.cmd (L250–271). They can disagree on edge cases (PATHEXT, non-spawnable shims).

Fix: Share one launcher-resolution helper for both the stale hint and CLI spawn paths.