feat(#2100): drive Windsurf through the EoS descriptor + wire Cascade's blocking hook bus (ADR-1239)

Fold all 10 residual isWindsurf branches in bin/install.js onto descriptor-driven
hostBehaviors (byte-parity — no fold changes any install output):
- 2 dead destructures dropped (uninstall, finishInstall); the dead
  `else if (isWindsurf)` legacy agent-loop arm removed (windsurf ∈
  _DESCRIPTOR_AGENTS_RUNTIMES → unreachable).
- skipSharedHooksInstall:true folds the two `!isWindsurf` shared-hooks exclusions.
- legacyDevinSkillsCleanup:true folds the `.devin`→`.windsurf` one-time cleanup gate.
- installsCommandBodiesForWorkflowDelegation:true folds the #1629 command-body copy
  (workflow-delegation target — load-bearing; local-install verified intact).
- verificationStyle:"windsurf-workflows" folds the workflow-count report.
- Corrected stale _LEGACY_SCAN_SUBDIR_NAMES + hooks-json manifest comments (cursor + windsurf).
Zero live runtime==='windsurf'/isWindsurf branches remain across bin/install.js,
install-engine.cts, surface.cts, runtime-artifact-conversion.cts (AC2 guard scans all four).

UPGRADE (Cascade hook bus): wire GSD's write/command safety guards into Windsurf's
native hook bus. New hooksSurface 'windsurf-hooks-json' (VALID_HOOKS_SURFACES 7→8, GATE A
profile-marker-only allowlist, the HooksSurface union) + writeWindsurfHooksJson
(Cursor-templated, Cascade's flat {hooks:{<event>:[{command}]}} shape) writing
.windsurf/hooks.json with two BLOCKING pre-hooks:
- pre_write_code → gsd-windsurf-pre-write.js: blocks writes to a file outside the
  active git worktree / into .git internals.
- pre_run_command → gsd-windsurf-pre-command.js: conservative destructive-command
  deny-list (rm -rf of root/home incl. sudo/env/path-prefixed forms; fork bombs;
  force-push refspec forms — HEAD:main, +main, --force/-f — to main/master/next).
Both use Cascade's protocol (stdin JSON, exit 2 + stderr to block, exit 0 to allow,
fail-open on error/timeout). Tokenize-based classifier (no catastrophic-backtracking regex;
4096-char cap) with the fail-closed false-positives fixed post-review.

The 4 advisory GSD guards + pre_mcp_tool_use + 5 post_* logging events are deliberately
NOT wired: Cascade has no context-injection channel for advisory hooks and GSD has no MCP
guard — porting them would be non-functional padding (documented; codebuddy #2098 / copilot
#2099 faithful-subset precedent). extendedHookEvents stays [].

Golden: the 2 guard scripts ship in the shared hook bundle (HOOKS_TO_COPY + the shared
managed-hooks-registry), exactly like cursor's 6 gsd-cursor-*.js scripts — so the 8
shared-bundle runtimes' fixtures gain the 2 inert windsurf scripts + the registry hash
(functionally inert for non-windsurf; the established cursor pattern). No install-output
change beyond that (the folds are byte-parity; skip-bundle runtimes untouched). New scripts
registered in managed-hooks-registry + build-hooks + INVENTORY. Tests: declarative-reference-
windsurf (adapter/axes/fail-closed + AC2 guard) + windsurf-hooks-bridge (live exit-2 blocking
+ allow/fail-open + ReDoS-bound + writer/reconcile/remove idempotency); VALID_HOOKS_SURFACES
pin updated to 8. Matrix hookBus delta + changeset (Changed). capability-registry regenerated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/INVENTORY.md

@@ -554,6 +554,8 @@ Full listing: `hooks/`.
 | `gsd-cursor-stop.js` | Cursor `stop` | Cursor-native verify-work reminder on agent stop (ADR-1239 / #2089) |
 | `gsd-cursor-subagent-start.js` | Cursor `subagentStart` | Cursor-native subagent context injection (ADR-1239 / #2089) |
 | `gsd-cursor-subagent-stop.js` | Cursor `subagentStop` | Cursor-native subagent completion reminder (ADR-1239 / #2089) |
+| `gsd-windsurf-pre-write.js` | Windsurf/Cascade `pre_write_code` | Blocking (exit-code-2) write-path guard — blocks a write resolving to a different git root than cwd, or inside `.git/` internals (ADR-1239 / #2100) |
+| `gsd-windsurf-pre-command.js` | Windsurf/Cascade `pre_run_command` | Blocking (exit-code-2) destructive-command guard — conservative deny-list (`rm -rf` root/home wipes, force-push to a protected branch) (ADR-1239 / #2100) |
 | `gsd-prompt-guard.js` | `PreToolUse` | Scans `.planning/` writes for prompt-injection patterns (advisory) |
 | `gsd-workflow-guard.js` | `PreToolUse` | Detects file edits outside GSD workflow context (advisory, opt-in) |
 | `gsd-read-guard.js` | `PreToolUse` | Advisory guard preventing Edit/Write on unread files |