refactor(3597): extract captureConsole + toPosixPath to helpers; dedup makeTmp wrappers; CLAUDE.md MemPalace

## Helper deduplication (16 files)

Two genuinely-duplicated test helpers extracted to tests/helpers.cjs:

- captureConsole(fn) → {stdout, stderr} with ANSI strip + exception
  re-throw after console restore (preserves the #2775 CR contract).
  Removed from 6 bug-N test files (bug-2775, bug-2829, bug-3033,
  bug-3211, bug-3231, bug-3359) where the implementation was either
  byte-identical or trivially-different. installer-migration-install-
  integration's captureConsole has a different signature ({value,
  output}) and stays as-is.

- toPosixPath(p) → p with path.sep → '/'. Returns input unchanged if
  null/undefined for safe optional-chain composition. Replaces the
  local normalizePath in bug-3491-nested-git-worktree (the
  prune-orphaned-worktrees inline normalizeSlashes was already swapped
  for canonicalPath in the cluster-J batch).

## makeTmp/mkScratch wrappers (8 files)

Reduced each local wrapper from a 3-line fs.mkdtempSync(path.join(
os.tmpdir(), ...)) block to a 1-line arrow delegating to
createTempDir (already in helpers.cjs). Bug-number prefix conventions
stay local for readability:

  - bug-2256, bug-2794, feat-3023, feat-3024 → `gsd-<bug>-${prefix}-`
  - bug-3288 → makeTmpDir = createTempDir (identity)
  - bug-3571 → 'gsd-3571-' (no parameter)
  - feat-3595 → mkScratch = `fs-fault-${name}-`
  - project-root-generator → 'gsd-parity-'

bug-3288 also collapsed local rmTmpDir into `cleanup` from helpers
(removes a separate inline rmSync site).

## CLAUDE.md — MemPalace protocol

Adds explicit instruction to call mempalace_status at session start
and mempalace_search / mempalace_kg_query before answering questions
about people, past work, or prior decisions in this project.

## Why this is a real consolidation

Initial survey suggested the bug-N test files could be parameterized
into one install-end-to-end.test.cjs — that turned out to oversell the
savings (~200 LOC on 2238) and to bury per-bug fixture context in a
table. The genuinely duplicated surface was the helpers themselves:
captureConsole copy-pasted ~6×, makeTmp variant copy-pasted ~8×.
Extracting them retires ~170 LOC of pure copy-paste without changing
any test semantics.

Validated: holodeck (ubuntu docker) 11232/0 pass; ratchet guard
still 7/7 at baseline.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/bug-3491-nested-git-worktree.test.cjs

@@ -42,11 +42,9 @@ const WORKFLOW_PATH = path.join(
 // ─── Helper: create outer git repo with a nested workstream subdir ─────────
 
 // On Windows the runtime emits forward slashes (git's convention) while
-// path.join produces backslashes — normalize both sides before any
-// equality comparison against the handler's git_worktree_root.
-function normalizePath(p) {
-  return p == null ? p : p.split(path.sep).join('/');
-}
+// path.join produces backslashes — normalize both sides via the shared
+// toPosixPath helper before any equality comparison.
+const { toPosixPath: normalizePath } = require('./helpers.cjs');
 
 function createOuterRepoWithSubdir(prefix = 'bug-3491-') {
   const outer = fs.mkdtempSync(path.join(os.tmpdir(), prefix));