fix: pre-landing review fixes for the Aside-first branch

Review army + adversarial passes (Claude and Codex) on the merged branch:

setup
- _prune_stale_generated scans the host dirs too (the generator already
  removed the render before setup ran, so the host branch was dead), skips
  symlinks in the render tree (rm -rf on a slash-terminated link empties its
  target), removes a host symlink only when it resolves into gstack, cleans a
  bannered real dir through _cleanup_weak_dir, recognizes frontmatter-renamed
  skills, and logs through log. The always-run codex render passes every host
  dir that may link to it.
- NEEDS_BUILD checks all three binaries (with $_EXE) and lib/ sources; the
  browser hint and the bootstrap summary honor GSTACK_SKIP_ASIDE, treat a
  requested skip as a request, and derive one skill list.

lib/aside-render.ts + bin/gstack-render.ts
- The loopback server carries a per-render secret path, checks containment on
  the real path (symlink escapes are 403), and rejects malformed encoding.
- Inline eval results are one base64 line, so page text cannot forge
  ASIDE_DIR= or the sentinel; the last ASIDE_DIR wins.
- runProc escalates SIGTERM to SIGKILL, bounds every wait, and clears every
  timer (an uncleared one kept gstack-render alive after printing OK).
- renderTmpDir refuses a shared /tmp name owned by someone else; the work dir
  and server are created inside try; goto's budget follows the render budget.
- probeAside classifies a present-but-failing CLI as ASIDE_NOT_RUNNING like
  the skills' bash probe; render() retries on gstack's own browser when Aside
  could not start or its private CDP bridge is gone (never on a page error
  or a timeout of a running script); the CLI reports the engine that actually
  rendered, exits 0 on --help, rejects non-numeric flags, documents
  --wait-timeout, fences EVAL/PAGE_ERRORS as untrusted content, and names the
  daemon's cookie-import JS lock remedy.
- The browse path passes --scale only when asked (a scale change rebuilds
  the daemon context) and restores the viewport after a sized screenshot.

resolvers / templates
- The bash probe honors GSTACK_SKIP_ASIDE and has a perl deadline on stock
  macOS; .local is no longer LOCAL (mDNS); same-origin filters compare parsed
  origins; link status is HEAD-checked only on LOCAL targets; every
  aside exec goes through the receipted _aside_exec prelude
  ({{ASIDE_EXEC_PRELUDE}}), including nine template blocks that called it
  bare; the design sketch and diagram staging use private directories.
- The generator prunes only bannered renders and never a host whose
  generation failed.

Docs, stale comments and dead code cleaned; goldens re-rendered; tests
updated and added for every behavior above.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

qa/sections/qa-patterns.md

@@ -108,18 +108,19 @@ console.log("GSTACK_STEP_OK");
 
 Then copy the screenshot out of the printed directory and show it: `cp "<ASIDE_DIR>/initial.jpg" "$REPORT_DIR/screenshots/initial.jpg"`, then Read it.
 
-Map the navigation structure with the links script (same-origin, read-only HEAD requests with the user's cookies):
+Map the navigation structure with the links script (same-origin; HEAD status checks only on a LOCAL target — on a real site the user's cookies would ride every request, so links print as `LINK ?` unfetched):
 
 ```bash
 aside repl '
 const pg = await openTab("<target-url>");
-const links = await pg.evaluate(() => [...new Set([...document.querySelectorAll("a[href]")].map(a => a.href))].filter(h => h.startsWith(location.origin) && !/logout|signout|delete|remove|cancel|unsubscribe/i.test(h)));
-for (const l of links) { const r = await fetch(l, { method: "HEAD" }).catch(e => ({ status: "ERR " + e.message })); console.log("LINK", r.status, l); }
+const links = await pg.evaluate(() => [...new Set([...document.querySelectorAll("a[href]")].map(a => a.href))].filter(h => new URL(h).origin === location.origin && !/logout|signout|delete|remove|cancel|unsubscribe/i.test(h)));
+const local = await pg.evaluate(() => /^(localhost|127\.0\.0\.1|0\.0\.0\.0|::1|\[::1\])$|\.(localhost|test)$/.test(location.hostname));
+for (const l of links) { if (!local) { console.log("LINK ?", l); continue; } const r = await fetch(l, { method: "HEAD" }).catch(e => ({ status: "ERR " + e.message })); console.log("LINK", r.status, l); }
 await closeTab(pg); console.log("GSTACK_STEP_OK");
 '
 ```
 
-Every `LINK` line with a 4xx/5xx or `ERR` status is a broken link for the Links score.
+Every `LINK` line with a 4xx/5xx or `ERR` status is a broken link for the Links score; `LINK ?` lines were not fetched (non-local target) and count as unverified, not broken.
 
 **Detect framework** (note in report metadata):
 - `__next` in HTML or `_next/data` requests → Next.js