chore: regenerate SKILL.md docs + golden fixtures (single regen for the template block)

Pure generator output for the six template/resolver commits above (learnings
capture, untrusted-content warning, review paths, pair-agent consent, codex
resume note, upgrade ff-only, brain-sync block) — bun run gen:skill-docs +
--host codex + --host factory, with the three ship golden fixtures refreshed
per the documented procedure. The three sidecar-path pins in
gen-skill-docs.test.ts move to the new installed-root/$GSTACK_ROOT contract
(#2518). Restores template freshness; full suite green from here.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

codex/SKILL.md

@@ -514,7 +514,7 @@ _BRAIN_SYNC_MODE=$("$_BRAIN_CONFIG_BIN" get artifacts_sync_mode 2>/dev/null || e
 _GBRAIN_MCP_MODE="none"
 _GBRAIN_MCP_ENTRY=""
 if command -v jq >/dev/null 2>&1 && [ -f "$HOME/.claude.json" ]; then
-  _GBRAIN_MCP_ENTRY=$(jq -c --arg cwd "$PWD" '.mcpServers.gbrain // ((.projects // {}) | to_entries | map(select((.key as $k | $cwd == $k or ($cwd | startswith($k + "/"))) and ((try .value.mcpServers.gbrain catch null) != null))) | sort_by(.key | length) | last | .value.mcpServers.gbrain) // empty' "$HOME/.claude.json" 2>/dev/null)
+  _GBRAIN_MCP_ENTRY=$(jq -c --arg cwd "$PWD" '((.projects // {}) | to_entries | map(select((.key as $k | $cwd == $k or ($cwd | startswith($k + "/"))) and ((try .value.mcpServers.gbrain catch null) != null))) | sort_by(.key | length) | last | .value.mcpServers.gbrain) // .mcpServers.gbrain // empty' "$HOME/.claude.json" 2>/dev/null)
   _GBRAIN_MCP_TYPE=$(printf '%s' "$_GBRAIN_MCP_ENTRY" | jq -r '.type // .transport // empty' 2>/dev/null)
   case "$_GBRAIN_MCP_TYPE" in
     url|http|sse) _GBRAIN_MCP_MODE="remote-http" ;;
@@ -554,7 +554,10 @@ if [ "$_GBRAIN_MCP_MODE" = "remote-http" ]; then
   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 ' ')
+  # Spool-dir queue (one file per record); legacy .brain-queue.jsonl lines are
+  # counted too until the drain migrates them.
+  [ -d "$_GSTACK_HOME/.brain-queue.d" ] && _BRAIN_QUEUE_DEPTH=$(find "$_GSTACK_HOME/.brain-queue.d" -maxdepth 1 -name '*.json' 2>/dev/null | wc -l | tr -d ' ')
+  [ -f "$_GSTACK_HOME/.brain-queue.jsonl" ] && _BRAIN_QUEUE_DEPTH=$(( _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 "$_GSTACK_HOME/.brain-last-push" 2>/dev/null || echo never)
   echo "ARTIFACTS_SYNC: mode=$_BRAIN_SYNC_MODE | last_push=$_BRAIN_LAST_PUSH | queue=$_BRAIN_QUEUE_DEPTH"
@@ -772,7 +775,13 @@ Escalate after 3 failed attempts, uncertain security-sensitive changes, or scope
 
 ## Operational Self-Improvement
 
-Before completing, if you discovered a durable project quirk or command fix that would save 5+ minutes next time, log it:
+Before completing, review the session for durable learnings and log each one —
+this step ALWAYS runs, it is not conditional on something feeling noteworthy
+(#2402: 43 of 44 learnings came from explicit /learn because "if you
+discovered" read as optional). A durable learning is a project quirk, command
+fix, pitfall, or pattern that would save 5+ minutes in a future session. If
+the review genuinely surfaces none, state "No durable learnings this session"
+in your completion summary — an explicit empty result, not a skipped step.
 
 ```bash
 ~/.claude/skills/gstack/bin/gstack-learnings-log '{"skill":"SKILL_NAME","type":"operational","key":"SHORT_KEY","insight":"DESCRIPTION","confidence":N,"source":"observed"}'
@@ -1578,6 +1587,14 @@ elif [ "$_CODEX_EXIT" != "0" ]; then
 fi
 ```
 
+**Session-cost reality (#2387, measured):** every `codex exec` call — resumed
+or fresh — pays Codex's ~21K-token session prelude (its skill catalogue +
+instructions); `resume` does NOT amortize it (a measured resume came in
+slightly ABOVE a fresh call). Resume buys conversational continuity, never
+token savings. So: prefer ONE codex call per skill where the workflow allows,
+batch questions into that call, and reach for resume only when the follow-up
+genuinely needs the prior session's context.
+
 For a **resumed session** (user chose "Continue"):
 ```bash
 _REPO_ROOT=$(git rev-parse --show-toplevel) || { echo "ERROR: not in a git repo" >&2; exit 1; }