feat(grunt/tui): hivemind sidebar + clickable #N ticket refs - #12

* feat(grunt/tui): hivemind sidebar + clickable #N ticket refs

Refs hivemind anomalyco#229 + anomalyco#233 — make hivemind state ambient in the gruntcode TUI
so Nik has operator awareness without window-switching to hivemind-ui.

New 'hivemind' panel inside the existing right sidebar, between the session
title block and the gruntcode footer. Polls hivemind-api on
localhost:7890 every 2s for:

- This peer's status (id, summary, wakeable flag, last_seen)
- Live peers (other alive sessions, with summaries)
- Unread inbox (DMs targeting this peer; client-side filtered, doesn't
  auto-markRead just from polling)
- Board pulse (open / claimed / stale counts; high-prio + mine highlights)

When hivemind-api is down, shows a 'api offline' placeholder. When the
session isn't announced (no --peer-id), shows 'not announced yet'.

Wake-log section deferred — hivemind-api doesn't yet expose
/api/wake-log; filed as a follow-up. The other 4 sections cover the
core ambient-awareness use case.

New files:
- packages/opencode/src/cli/cmd/tui/context/hivemind.tsx — solid-js
  context with poll loop + state store
- packages/opencode/src/cli/cmd/tui/routes/session/hivemind-sections.tsx
  — the 4 rendered sections

Wired:
- app.tsx wraps the tree in HivemindProvider
- sidebar.tsx renders <HivemindSections /> in the existing scrollbox

In the assistant message TextPart, before passing markdown to the renderer,
linkify hivemind ticket refs: 'anomalyco#229' becomes the markdown link
'[anomalyco#229](http://localhost:5173/tasks/229)'. The markdown renderer styles
links with theme.markdownLink (blue/cyan); terminals supporting OSC 8
(iTerm2, kitty) make the link clickable. Falls back to colored-but-non-
clickable in older terminals.

Regex `(^|[^\w/#])#(\d{1,5})\b` avoids false positives on hex colors
(#fff has letters), already-linked refs ([anomalyco#229] won't match because
prev char is '['), and longer-than-5-digit numbers.

URL base configurable via HIVEMIND_UI_BASE env (defaults to
http://localhost:5173 to match the running hivemind-ui dev server).

bun typecheck clean. Local install via scripts/install-local.sh works;
binary reports v1.15.10-grunt.7-5-g18407fd53-dirty-local.

* feat(grunt/tui): bare gruntcode auto-lands in session route (sidebar visible from first frame)

Refs hivemind anomalyco#229. The hivemind sidebar lives inside the session route — so
bare `gruntcode` landing on the home/splash route HID the sidebar until the
user submitted their first prompt. Nik's intent was 'open gruntcode tab and
already be in that view, ready to type'.

This effect auto-creates an empty session and navigates when:
- No explicit --session / --continue / --fork
- No --prompt (--prompt has its own auto-submit path on home)
- Currently on home route
- sync + model are ready (session.create requires agent + model)

Escape hatch: OPENCODE_DISABLE_AUTO_SESSION=1 keeps legacy 'land on splash'
behavior for users who prefer the home route.

…gle <markdown> (no flicker) (anomalyco#331)

Definitive fix after exhausting the alternatives (all build-tested):
- single <markdown> is the ONLY flicker-free renderer; per-block split flickered
  on stream + lost formatting.
- markdown [#N](url) links always leak the URL in this app (no tree-sitter);
  inline <a> can't live inside <markdown>.
- JS-side column estimation drifted (hover 'all over the place').

So: keep ONE <markdown> rendering plain  (clean, full formatting, wrap-correct,
flicker-free), and resolve hover/click by reading the renderer's actual FRAMEBUFFER —
renderer.currentRenderBuffer.buffers.char is a public Uint32Array indexed y*width+x.
ticketIdAtCell() inspects the characters painted under the cursor and returns the
#N id (with the same boundary rules as the text regex: rejects foo#12, ##12, #fff).
Pixel-accurate (uses rendered cells, not a reconstruction), null off-ref so the
hover card closes. Drives the existing TicketHoverCard; onMouseUp opens hivemind-ui.

10 framebuffer hit-test unit tests + TUI suite (143 pass) + typecheck green.

…-process (anomalyco#331)

Refs render as plain #N inside <markdown> (a markdown link leaks its URL), so
they were base text color. Recolor the painted #N cells in a renderer
post-process (renderer.addPostProcessFn): single buffer scan re-drawing matched
#N runs in theme.markdownLink + underline. Same boundary rules as the hit-test
(skips foo#12 / ##12 / #fff). Theme proxy is read each frame so it tracks theme
switches.

4 recolor unit tests (+ existing 10 hit-test) + TUI suite (147 pass) + typecheck green.