test: regression suite + E2E for v1.27.0.0 rename

Three new regression tests guard the rename's blast radius (per codex
Findings #1, #8, #9, #12):

- test/no-stale-gstack-brain-refs.test.ts: greps bin/, scripts/, *.tmpl,
  test/ for forbidden identifiers (gstack-brain-init, gbrain_sync_mode);
  fails CI if any non-allowlisted file references them.
- test/post-rename-doc-regen.test.ts: confirms gen-skill-docs output has
  no stale references in any */SKILL.md (the cross-product blind spot).
- test/setup-gbrain-path4-structure.test.ts: structural lint over the
  Path 4 prose contract — STOP gates after verify failure, never-write-
  token rules, mode-aware CLAUDE.md block, bearer always via env-var.

Two new gate-tier E2E tests (deterministic stub HTTP server, fixed inputs):

- test/skill-e2e-setup-gbrain-remote.test.ts: Path 4 happy path. Stubs
  an HTTP MCP server, drives the skill via Agent SDK with a stubbed
  bearer, asserts claude.json gets the http MCP entry, CLAUDE.md gets
  the remote-http block, the secret token NEVER leaks to CLAUDE.md.
- test/skill-e2e-setup-gbrain-bad-token.test.ts: stub server returns 401;
  asserts the AUTH classifier hint surfaces, no MCP registration occurs,
  CLAUDE.md is unchanged. Regression guard for the "verify failed → STOP"
  rule.

touchfiles.ts: setup-gbrain-remote and setup-gbrain-bad-token added at
gate-tier so CI catches Path 4 regressions on every PR.

Plus a few comment refs flipped: bin/gstack-jsonl-merge, bin/gstack-timeline-log
(legacy gstack-brain-init mentions in headers).

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

sync-gbrain/SKILL.md

@@ -768,6 +768,22 @@ Before doing anything, check that /setup-gbrain has been run on this Mac.
 ~/.claude/skills/gstack/bin/gstack-gbrain-detect 2>/dev/null
 ```
 
+**Remote-MCP mode (Path 4 of /setup-gbrain):** if `gbrain_mcp_mode=remote-http`,
+this skill is a graceful no-op. The brain server's own indexing cadence
+handles code import + search refresh; this Mac doesn't run a local gbrain
+CLI to drive `gbrain sources add` / `sync --strategy code`. Print:
+
+> "Remote MCP detected (Path 4). /sync-gbrain is local-mode-only in V1.
+> Your brain server (`<host>` from claude.json) handles indexing on its own
+> cadence. If indexing seems stale, ping your brain admin or trigger a
+> manual sync there. To wire `/sync-gbrain` through MCP tools (when gbrain
+> ships `mcp__gbrain__sources_add` and friends), see the v1.27.0.0+
+> follow-on TODO."
+
+Then exit cleanly. Do NOT proceed to Step 2.
+
+For local-stdio mode and unconfigured states:
+
 If `gbrain_on_path=false` OR `gbrain_config_exists=false` OR CLAUDE.md does
 not contain `## GBrain Configuration (configured by /setup-gbrain)`, STOP and
 tell the user:

sync-gbrain/SKILL.md.tmpl

@@ -66,6 +66,22 @@ Before doing anything, check that /setup-gbrain has been run on this Mac.
 ~/.claude/skills/gstack/bin/gstack-gbrain-detect 2>/dev/null
 ```
 
+**Remote-MCP mode (Path 4 of /setup-gbrain):** if `gbrain_mcp_mode=remote-http`,
+this skill is a graceful no-op. The brain server's own indexing cadence
+handles code import + search refresh; this Mac doesn't run a local gbrain
+CLI to drive `gbrain sources add` / `sync --strategy code`. Print:
+
+> "Remote MCP detected (Path 4). /sync-gbrain is local-mode-only in V1.
+> Your brain server (`<host>` from claude.json) handles indexing on its own
+> cadence. If indexing seems stale, ping your brain admin or trigger a
+> manual sync there. To wire `/sync-gbrain` through MCP tools (when gbrain
+> ships `mcp__gbrain__sources_add` and friends), see the v1.27.0.0+
+> follow-on TODO."
+
+Then exit cleanly. Do NOT proceed to Step 2.
+
+For local-stdio mode and unconfigured states:
+
 If `gbrain_on_path=false` OR `gbrain_config_exists=false` OR CLAUDE.md does
 not contain `## GBrain Configuration (configured by /setup-gbrain)`, STOP and
 tell the user: