Reflect run status in tab title + favicon (BEN-50)

[benSepanski]

Context

BEN-50: src/web/index.html hardcoded <title>Symphony</title> and shipped no favicon, so users keeping Symphony open alongside tracker / docs / logs had no at-a-glance signal that a run went red, and multiple run-detail tabs were indistinguishable.

TL;DR

Each top-level route now sets its own tab title via a tiny useDocumentChrome hook, and ships a monotone SVG favicon that flips red on a recent failure.

Summary

• New src/web/documentTitle.ts — pure helpers (dashboardTitle, runDetailTitle, dashboardFaviconColor, runFaviconColor, findMostRecentFailure, buildFaviconHref). 14 unit tests in documentTitle.test.ts.
• New src/web/useDocumentChrome.ts — thin React hook that writes document.title and patches a single <link rel="icon">; lazily creates the link tag if the page didn't ship one.
• Dashboard.tsx — derives title from runs + a 30 s now tick. Symphony → ● N running · Symphony → ✖ <issue> <status> · Symphony for failures within the 5 min window.
• RunDetail.tsx — <issue> · <status> · Symphony; favicon flips red while the run is failed / rate_limited.
• Search.tsx — <query> · search · Symphony (or just search · Symphony) so the route doesn't inherit a stale dashboard title.
• src/web/index.html — ships the neutral SVG favicon up front so the first paint is already correct; runtime updates the same <link> for state changes.
• docs/FRONTEND.md — documents the per-route title pattern + 5 min failure-escalation window.

Demo

n/a — automated cron run; no browser MCP in this environment. Manual smoke-test path: pnpm dev WORKFLOW.md --mock, open the dashboard with a live mock run (● 1 running · Symphony), trigger the crash scenario and confirm the tab title escalates to ✖ <issue> failed · Symphony and the favicon flips rose; open two run-detail tabs and confirm each tab title differs.

Alternatives

• Lift runs into App.tsx and set the title from there — rejected: requires re-plumbing every Dashboard data path through a shared store; the per-view hook keeps each route owning its own state.
• requestAnimationFrame to update title — rejected: BEN-50 acceptance explicitly calls out that backgrounded tabs must still update, and rAF is paused when the tab is hidden. setInterval keeps the failure window honest.
• Ship a real PNG favicon under public/ — rejected: a 64×64 SVG data URL is two lines of code, recolorable at runtime, and avoids a binary asset in the repo.
• Use the Notification API for run-finished events (mentioned in the ticket) — deferred. Tab-chrome alone covers the acceptance criteria; opt-in notifications belong in a follow-up alongside BEN-9's server-side hook.

Test Plan

• pnpm all — typecheck + fmt:check + lint + test + eval (134 unit + 5 eval, all green)
• pnpm build:web — bundle builds (176 ms, 228.86 kB)
• New documentTitle.test.ts covers running-count titles, recent-failure escalation, stale-failure expiration, missing/future finishedAt, per-route favicon color, SVG data URL encoding, and findMostRecentFailure ordering.

---

Generated by Claude Code