fix(web): address self-review findings on #103 (master-safe defaults + hardening)

Make the branch genuinely master-mergeable and fix several review findings:

- Defaults are now prod-safe: CODEMAN_INSTANCE defaults to '' (→ ~/.codeman,
  -L codeman) and the web port back to 3000, so an existing install upgrades
  cleanly. Port also honors a new CODEMAN_PORT env var. Run the beta isolated
  alongside prod with scripts/run-beta.sh (CODEMAN_INSTANCE=beta + PORT 5000).
- .gitignore: anchor the root `public` symlink rule to `/public` (a bare
  `public` also swallowed src/web/public, silently un-staging new web assets);
  ignore the gesture wasm/model binaries explicitly instead.
- span-displays: add a macOS-only guard (400 elsewhere instead of spawning a
  bash that fails invisibly); extract resolveSpanUrl() for unit testing.
- server.ts: memoize asset-version stat() calls (~1s TTL) so each index render
  doesn't re-stat every script/link tag.
- styles.css: hide the multi-monitor button in solo (detached) windows.
- app.js: require two consecutive unanswered roll-calls before redocking, so a
  timer-throttled background popup isn't wrongly un-marked.
- index.html: make the "skip to terminal" link base-href-safe (onclick scroll)
  so it doesn't navigate to the dashboard from a /session/:id window.
- Tests: test/config/instance.test.ts, test/routes/system-span-displays.test.ts.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

scripts/fetch-gesture-assets.mjs

@@ -3,8 +3,8 @@
  * gesture-recognizer model) into src/web/public/gesture/ so Codeman can serve
  * them same-origin (a browser content-blocker otherwise blocks the public CDNs
  * and the overlay fails to start). These are large binaries (~27 MB) kept OUT of
- * git (the bare `public` rule in .gitignore covers them); they are fetched here
- * at install (postinstall) and build time instead.
+ * git (ignored explicitly via `src/web/public/gesture/wasm/` + `*.task` in
+ * .gitignore); they are fetched here at install (postinstall) and build time.
  *
  * Idempotent: skips files already present. Non-fatal: the gesture overlay is
  * opt-in (CODEMAN_GESTURE=1), so a fetch failure only warns — it must not break

scripts/run-beta.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+#
+# run-beta.sh — launch a BETA Codeman isolated from a production instance.
+#
+# Codeman's data dir (~/.codeman) and tmux socket (-L codeman) are process-wide
+# and shared by every instance on the machine. The code now DEFAULTS to that
+# production layout on port 3000 (safe for master / existing installs), so a beta
+# build no longer isolates itself automatically — this wrapper opts it in:
+#
+#   CODEMAN_INSTANCE=beta  → data dir ~/.codeman-beta + tmux socket codeman-beta
+#   CODEMAN_PORT=5000      → listen on 5000 instead of 3000
+#
+# Result: the beta runs side-by-side with prod and can never discover/attach to
+# prod's live tmux sessions or clobber prod's state.json. Override either var to
+# run additional named instances, e.g. CODEMAN_INSTANCE=foo CODEMAN_PORT=5050.
+#
+# Usage:  ./scripts/run-beta.sh [extra `codeman web` flags]
+# Build first (the beta runs the compiled dist):  npm run build
+
+set -euo pipefail
+
+export CODEMAN_INSTANCE="${CODEMAN_INSTANCE:-beta}"
+export CODEMAN_PORT="${CODEMAN_PORT:-5000}"
+
+DIST="$(cd "$(dirname "$0")/.." && pwd)/dist/index.js"
+if [ ! -f "$DIST" ]; then
+  echo "dist not found at $DIST — run 'npm run build' first." >&2
+  exit 1
+fi
+
+echo "Starting beta Codeman: instance='$CODEMAN_INSTANCE' (~/.codeman-$CODEMAN_INSTANCE, -L codeman-$CODEMAN_INSTANCE) on port $CODEMAN_PORT"
+exec node "$DIST" web "$@"