refactor: rename gbrain_sync_mode → artifacts_sync_mode (v1.27.0.0 prep)

Hard rename, no dual-read alias (codex Finding D4). The on-disk migration
script (Phase C, separate commit) renames the config key in users'
~/.gstack/config.yaml and any CLAUDE.md blocks.

Touched call sites:
- bin/gstack-config defaults + validation + list/defaults output
- bin/gstack-gbrain-detect (gstack_brain_sync_mode field still emitted
  with the same name for downstream-tool compat; reads new key)
- bin/gstack-brain-sync, bin/gstack-brain-enqueue, bin/gstack-brain-uninstall
- bin/gstack-timeline-log (comment ref)
- scripts/resolvers/preamble/generate-brain-sync-block.ts: renames key,
  branches on gbrain_mcp_mode=remote-http to emit "ARTIFACTS_SYNC:
  remote-mode (managed by brain server <host>)" instead of the local
  mode/queue/last_push line (codex Finding #11)
- bin/gstack-brain-restore + bin/gstack-gbrain-source-wireup: read
  ~/.gstack-artifacts-remote.txt with ~/.gstack-brain-remote.txt fallback
  during the migration window
- bin/gstack-artifacts-init: tolerant of unrecognized URL forms (local
  paths, file://, self-hosted gitea) so test infrastructure and unusual
  remotes work without canonicalization
- test/brain-sync.test.ts: gstack-brain-init → gstack-artifacts-init
- test/skill-e2e-brain-privacy-gate.test.ts: artifacts_sync_mode keys
- test/gen-skill-docs.test.ts: budget 35K → 36.5K for the new MCP-mode
  probe in the preamble resolver
- health/SKILL.md.tmpl, sync-gbrain/SKILL.md.tmpl: comment + verdict line

Hard delete:
- bin/gstack-brain-init (replaced by bin/gstack-artifacts-init in v1.27.0.0)
- test/gstack-brain-init-gh-mock.test.ts (replaced by gstack-artifacts-init.test.ts)

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

scripts/resolvers/preamble/generate-brain-sync-block.ts

@@ -1,19 +1,24 @@
 /**
- * gbrain-sync preamble block.
+ * artifacts-sync preamble block (renamed from gbrain-sync in v1.27.0.0).
  *
  * Emits bash that runs at every skill invocation:
  *   0. Live gbrain-availability hint (per /plan-eng-review): when gbrain is
  *      configured, emit one of two variants (steady-state vs empty-corpus
  *      emergency). Zero context cost when gbrain is not configured.
- *   1. If ~/.gstack-brain-remote.txt exists AND ~/.gstack/.git is missing,
- *      surface a restore-available hint (does NOT auto-run restore).
- *   2. If sync is on, run `gstack-brain-sync --once` (drain + push).
+ *   1. If ~/.gstack-artifacts-remote.txt (or legacy ~/.gstack-brain-remote.txt
+ *      during the v1.27.0.0 migration window) exists AND ~/.gstack/.git is
+ *      missing, surface a restore-available hint (does NOT auto-run restore).
+ *   2. If sync is on, run `gstack-brain-sync --once` (drain + push). The
+ *      script keeps its old name; only the config-key + state-file names flip.
  *   3. On first skill of the day (24h cache via .brain-last-pull):
  *      `git fetch` + ff-only merge (JSONL merge driver handles conflicts).
- *   4. Emit a `BRAIN_SYNC:` status line so every skill surfaces health.
+ *   4. Emit an `ARTIFACTS_SYNC:` status line so every skill surfaces health.
+ *      In remote-MCP mode, the line reads `ARTIFACTS_SYNC: remote-mode
+ *      (managed by brain server <host>)` since this machine doesn't sync
+ *      anything locally — the brain admin's server pulls from GitHub/GitLab.
  *
  * Also emits prose instructions for the host LLM to fire a one-time privacy
- * stop-gate via AskUserQuestion when gbrain_sync_mode is unset and gbrain
+ * stop-gate via AskUserQuestion when artifacts_sync_mode is unset and gbrain
  * is available on the host.
  *
  * Block emitted across all tiers. Internal bash short-circuits when feature
@@ -26,11 +31,17 @@ import type { TemplateContext } from '../types';
 
 export function generateBrainSyncBlock(ctx: TemplateContext): string {
   const isBrainHost = ctx.host === 'gbrain' || ctx.host === 'hermes';
-  return `## GBrain Sync (skill start)
+  return `## Artifacts Sync (skill start)
 
 \`\`\`bash
 _GSTACK_HOME="\${GSTACK_HOME:-$HOME/.gstack}"
-_BRAIN_REMOTE_FILE="$HOME/.gstack-brain-remote.txt"
+# Prefer the v1.27.0.0 artifacts file; fall back to brain file for users
+# upgrading mid-stream before the migration script runs.
+if [ -f "$HOME/.gstack-artifacts-remote.txt" ]; then
+  _BRAIN_REMOTE_FILE="$HOME/.gstack-artifacts-remote.txt"
+else
+  _BRAIN_REMOTE_FILE="$HOME/.gstack-brain-remote.txt"
+fi
 _BRAIN_SYNC_BIN="${ctx.paths.binDir}/gstack-brain-sync"
 _BRAIN_CONFIG_BIN="${ctx.paths.binDir}/gstack-config"
 
@@ -63,13 +74,26 @@ if [ -f "$_GBRAIN_CONFIG" ] && command -v gbrain >/dev/null 2>&1; then
   fi
 fi
 
-_BRAIN_SYNC_MODE=$("$_BRAIN_CONFIG_BIN" get gbrain_sync_mode 2>/dev/null || echo off)
+_BRAIN_SYNC_MODE=$("$_BRAIN_CONFIG_BIN" get artifacts_sync_mode 2>/dev/null || echo off)
+
+# Detect remote-MCP mode (Path 4 of /setup-gbrain). Local artifacts sync is
+# a no-op in remote mode; the brain server pulls from GitHub/GitLab on its
+# own cadence. Read claude.json directly to keep this preamble fast (no
+# subprocess to claude CLI on every skill start).
+_GBRAIN_MCP_MODE="none"
+if command -v jq >/dev/null 2>&1 && [ -f "$HOME/.claude.json" ]; then
+  _GBRAIN_MCP_TYPE=$(jq -r '.mcpServers.gbrain.type // .mcpServers.gbrain.transport // empty' "$HOME/.claude.json" 2>/dev/null)
+  case "$_GBRAIN_MCP_TYPE" in
+    url|http|sse) _GBRAIN_MCP_MODE="remote-http" ;;
+    stdio) _GBRAIN_MCP_MODE="local-stdio" ;;
+  esac
+fi
 
 if [ -f "$_BRAIN_REMOTE_FILE" ] && [ ! -d "$_GSTACK_HOME/.git" ] && [ "$_BRAIN_SYNC_MODE" = "off" ]; then
   _BRAIN_NEW_URL=$(head -1 "$_BRAIN_REMOTE_FILE" 2>/dev/null | tr -d '[:space:]')
   if [ -n "$_BRAIN_NEW_URL" ]; then
-    echo "BRAIN_SYNC: brain repo detected: $_BRAIN_NEW_URL"
-    echo "BRAIN_SYNC: run 'gstack-brain-restore' to pull your cross-machine memory (or 'gstack-config set gbrain_sync_mode off' to dismiss forever)"
+    echo "ARTIFACTS_SYNC: artifacts repo detected: $_BRAIN_NEW_URL"
+    echo "ARTIFACTS_SYNC: run 'gstack-brain-restore' to pull your cross-machine artifacts (or 'gstack-config set artifacts_sync_mode off' to dismiss forever)"
   fi
 fi
 
@@ -89,22 +113,27 @@ if [ -d "$_GSTACK_HOME/.git" ] && [ "$_BRAIN_SYNC_MODE" != "off" ]; then
   "$_BRAIN_SYNC_BIN" --once 2>/dev/null || true
 fi
 
-if [ -d "$_GSTACK_HOME/.git" ] && [ "$_BRAIN_SYNC_MODE" != "off" ]; then
+if [ "$_GBRAIN_MCP_MODE" = "remote-http" ]; then
+  # Remote-MCP mode: local artifacts sync is a no-op (brain admin's server
+  # pulls from GitHub/GitLab). Show the user this is by design, not broken.
+  _GBRAIN_HOST=$(jq -r '.mcpServers.gbrain.url // empty' "$HOME/.claude.json" 2>/dev/null | sed -E 's|^https?://([^/:]+).*|\\1|')
+  echo "ARTIFACTS_SYNC: remote-mode (managed by brain server \${_GBRAIN_HOST:-remote})"
+elif [ -d "$_GSTACK_HOME/.git" ] && [ "$_BRAIN_SYNC_MODE" != "off" ]; then
   _BRAIN_QUEUE_DEPTH=0
   [ -f "$_GSTACK_HOME/.brain-queue.jsonl" ] && _BRAIN_QUEUE_DEPTH=$(wc -l < "$_GSTACK_HOME/.brain-queue.jsonl" | tr -d ' ')
   _BRAIN_LAST_PUSH="never"
   [ -f "$_GSTACK_HOME/.brain-last-push" ] && _BRAIN_LAST_PUSH=$(cat "$_GSTACK_HOME/.brain-last-push" 2>/dev/null || echo never)
-  echo "BRAIN_SYNC: mode=$_BRAIN_SYNC_MODE | last_push=$_BRAIN_LAST_PUSH | queue=$_BRAIN_QUEUE_DEPTH"
+  echo "ARTIFACTS_SYNC: mode=$_BRAIN_SYNC_MODE | last_push=$_BRAIN_LAST_PUSH | queue=$_BRAIN_QUEUE_DEPTH"
 else
-  echo "BRAIN_SYNC: off"
+  echo "ARTIFACTS_SYNC: off"
 fi
 \`\`\`
 
-${isBrainHost ? `If output shows \`BRAIN_SYNC: brain repo detected\`, offer \`gstack-brain-restore\` via AskUserQuestion; otherwise continue.` : ''}
+${isBrainHost ? `If output shows \`ARTIFACTS_SYNC: artifacts repo detected\`, offer \`gstack-brain-restore\` via AskUserQuestion; otherwise continue.` : ''}
 
-Privacy stop-gate: if output shows \`BRAIN_SYNC: off\`, \`gbrain_sync_mode_prompted\` is \`false\`, and gbrain is on PATH or \`gbrain doctor --fast --json\` works, ask once:
+Privacy stop-gate: if output shows \`ARTIFACTS_SYNC: off\`, \`artifacts_sync_mode_prompted\` is \`false\`, and gbrain is on PATH or \`gbrain doctor --fast --json\` works, ask once:
 
-> gstack can publish your session memory to a private GitHub repo that GBrain indexes across machines. How much should sync?
+> gstack can publish your artifacts (CEO plans, designs, reports) to a private GitHub repo that GBrain indexes across machines. How much should sync?
 
 Options:
 - A) Everything allowlisted (recommended)
@@ -115,11 +144,11 @@ After answer:
 
 \`\`\`bash
 # Chosen mode: full | artifacts-only | off
-"$_BRAIN_CONFIG_BIN" set gbrain_sync_mode <choice>
-"$_BRAIN_CONFIG_BIN" set gbrain_sync_mode_prompted true
+"$_BRAIN_CONFIG_BIN" set artifacts_sync_mode <choice>
+"$_BRAIN_CONFIG_BIN" set artifacts_sync_mode_prompted true
 \`\`\`
 
-If A/B and \`~/.gstack/.git\` is missing, ask whether to run \`gstack-brain-init\`. Do not block the skill.
+If A/B and \`~/.gstack/.git\` is missing, ask whether to run \`gstack-artifacts-init\`. Do not block the skill.
 
 At skill END before telemetry: