Reduce task panel density: collapsible sections and title-bar badge consolidation

[johannesjo]

Problem

A task column (default 520 px, min 300 px — TilingLayout.tsx:242-243) stacks up to ~10 info zones, none of which the user can collapse, and the title bar alone can carry a status dot plus seven badge types plus 4–5 icon buttons.

Zones, top to bottom (TaskPanel.tsx): coordinator banner + staged-notification sub-banner + macOS/Docker warning banner (:430-494), SubTaskStrip, TaskTitleBar (~50 px), TaskBranchInfoBar (~28 px), notes + changed-files split, shell section, AI terminal, steps section, prompt input.

Title-bar badges (TaskTitleBar.tsx:155-211): direct-branch, no-git, docker, imported, review, landing, verification — plus a CI-status micro-overlay on the push button (:262-325).

The only "collapse" today is implicit: the shell section shrinks to its 28 px toolbar when empty (TaskPanel.tsx:346-351). Notes, changed files, and steps always consume header rows even when unused. The coordinator banner stack can consume ~150 px before any content.

Related: #57 (prioritize terminal space), #175 (collapsible panel groups) — this issue is about vertical sections within a panel and the badge crowding; the terminal is clearly the primary object and the IA should say so.

Proposed fix

• Collapse toggle in each secondary section header (notes, changed files, steps, shells), persisted per task via the existing panelUserSize store — the flex-absorber tree already tolerates content-sized children (noPin in ResizablePanel.tsx:19-23).
• Default notes/steps collapsed on panels narrower than ~400 px.
• Consolidate the badge zoo into one status chip + an overflow ("+2") popover.
• Merge the coordinator status line into the SubTaskStrip row instead of a separate banner.

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From a full design/UX audit (2026-07-07); adversarially verified. Line numbers as of b342bbd (v1.12.0).