feat(debugger): extract philosophy block to shared reference (#2363) (#2364)

The gsd-debugger philosophy block contains 76 lines of evergreen
debugging disciplines (user-as-reporter, meta-debugging, cognitive
biases, restart protocol) that are not debugger-specific workflow
and are paid in context on every debugger dispatch.

Extracts to get-shit-done/references/debugger-philosophy.md, replaces
the inline block with a single @file include. Behavior-preserving.

Closes #2363

Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,9 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ## [Unreleased]
 
+### Changed
+- **`gsd-debugger` philosophy extracted to shared reference** — The 76-line `<philosophy>` block containing evergreen debugging disciplines (user-as-reporter framing, meta-debugging, foundation principles, cognitive-bias table, systematic investigation, when-to-restart protocol) is now in `get-shit-done/references/debugger-philosophy.md` and pulled into the agent via a single `@file` include. Same content, lighter per-dispatch context footprint (#2363)
+
 ### Fixed
 - **Shell hooks falsely flagged as stale on every session** — `gsd-phase-boundary.sh`, `gsd-session-state.sh`, and `gsd-validate-commit.sh` now ship with a `# gsd-hook-version: {{GSD_VERSION}}` header; the installer substitutes `{{GSD_VERSION}}` in `.sh` hooks the same way it does for `.js` hooks; and the stale-hook detector in `gsd-check-update.js` now matches bash `#` comment syntax in addition to JS `//` syntax. All three changes are required together — neither the regex fix alone nor the install fix alone is sufficient to resolve the false positive (#2136, #2206, #2209, #2210, #2212)