Correct the Worktrees docs and document shortcut pins

[selfcontained]

Nightly docs audit. Slice: the in-app Worktrees section (carried next_focus), plus the user-facing gaps in the diff since 9319fcaa.

Worktrees deep-dive

Audited docs-sections/worktrees.tsx against agents/workspace-prep.ts, shared/git/worktree.ts, agents/tmux/setup-script.ts, agents/archive.ts, and the create-dialog controls.

• Wrong claim fixed. "When creation fails" said the card shows an Attention badge. That badge renders only for status === "error" (agent-card-header.tsx); a worktree failure goes through markSetupFailed, which sets stopped, and the reconciler never revisits it because its query only selects running/stopping/creating/archiving. The real signal is the status line flipping to Blocked with the git error — now what the docs say.
• Fork point. Both launch paths fetch the starting branch from origin and fork the new branch from origin/<starting branch>; checking out the starting branch directly uses the local copy, and repos without an origin fall back to local. None of that was documented.
• Branch deletion on cleanup. Removing a worktree also deletes the branch Dispatch created for it, and answering Archive and remove worktree force-deletes it (git branch -D) along with unpushed commits. The section only described the directory.
• Terminal agents skip the dependency install in the setup script.

Verified-accurate and left alone: checkbox default/disabled state, .env copy, lockfile list and priority, sibling vs .dispatch/worktrees/ location, auto-generated branch name, per-cwd new-branch preference, partial-worktree cleanup on failure, and the archive keep/remove prompt.

Diff-driven

• media.tsx — shortcut pins can now be greyed out by the agent itself with the caption as the reason (Add a disabled state to shortcut pins #937).
• docs/03-api-spec.md — Terminal table was missing inject-text (Mobile fullscreen input: API-backed Paste/Submit buttons #935) and inject-pin/:pinId (Add shortcut pins: one-click prompt injection from the sidebar #930); added both with their body/error contract.
• tips.ts — new ambient tip for shortcut pins (Add shortcut pins: one-click prompt injection from the sidebar #930 shipped in 0.33.7 with no tip), deep-linked to a new media#media-sidebar anchor.

Deferred

Backlog gets the hold-badge-after-reload item (unchanged) and a note that the Archive and remove worktree button copy doesn't mention branch deletion — a product call, not a docs fix. Next run: the Repo Tools section against .dispatch/tools.json handling and lifecycle hooks.