Unify thread-list header actions and nested view controls

[brsbl]

Human comments

What was wrong

• Thread-list controls changed placement and menu structure between Pinned, projects, sections, machines, and loose threads. Worktree creation was hidden in its menu, and independently styled buttons made the sidebar harder to scan and maintain.
• Pinned could remain stuck above unrelated groups after its threads scrolled away. Compact worktree actions were inaccessible to touch, and reversing Updated at also reversed the existing active-first priority.

What changed

• All organizing headers share New thread followed by … on hover/focus, with visible controls on touch. Every header menu offers New project, New section, and compact nested Organize and Sort by menus, followed by existing context-specific actions.
• Organize is an exclusive choice and closes after selection. Sort remains open while tuning; selecting the current field reverses its arrow and direction while Updated at keeps active threads first. The additive sidebar.sortDirection preference uses the existing persistence, SDK, and CLI paths; default preserves prior ordering.
• Worktrees expose New thread inline, leaving Rename and Archive in their menu. Project editing actions are grouped together and separated from the existing Remove action. No creation destinations or destructive consequences change.
• Shared row-control components and semantic color/state tokens keep titles primary, grouping labels quieter, and controls secondary—including on hovered or selected rows. Navigation More uses a quieter resting color. Pinned now scrolls with its contents.
• Production Sidebar Overview stories replace the discarded prototype. The implementation removes superseded controls and delegates menu open/close state to the shared dropdown; the slimming pass removes 96 net lines (78 production, 18 tests) without changing approved behavior. Thread nesting, archive placement, plugin actions, and command-palette behavior are outside this change.

How you verified

• Remote CI passed at exact head cde7aeceeeb00958b82badfecd03437b04059f2d: build/typecheck/lint, all app/server/package/integration tests, and Linux/macOS package smoke. All 14 reported checks passed; native iOS and Node compatibility were workflow-skipped. No local CI-equivalent checks were run.
• Rebased onto main@e02f6e64cc7afdf490e70a662c6445b5b8dee407, retaining the prior merge resolutions. Tree comparison confirms the result is exactly the previous implementation plus upstream changes; the PR remains 27 files. Main's touch-visibility regression exercises the actual shared project controls through closed, open, and reclosed states.
• Exact-head Chrome for Testing 153.0.8010.36 verification passed at 1440×900 and 390×844: project menu ordering, Organize closing after selection, Sort remaining open during direction changes, and compact Back/close/reopen reset. Project controls remain visible and interactive with 36×36 touch targets before/during/after opening. Restored fixture preferences persist after reload.
• Earlier bounded QA covered project/machine/custom views, active-first sorting, light/dark control states, plugin styling, Pinned scrolling, worktree creation/rename, and collapsed touch controls. Retained regression tests cover action ordering, callbacks, focus behavior, menu lifecycle, preference validation, and active-first date sorting.
• Remaining verification limits: phone coverage is Chrome touch emulation, not native iOS/Safari. The existing compact retained-focus aria-hidden warning also occurred during close/reopen; the app root remained non-inert and exposed. The warning is not claimed fixed by this rebase.
• One cumulative review was completed previously; no second review was run. git diff --check passed.
• Screenshots use the same synthetic data, route /, project view, Updated at sorting, light theme, and open Atlas project menu. Before: exact merge base e02f6e64cc7afdf490e70a662c6445b5b8dee407. After: exact head cde7aeceeeb00958b82badfecd03437b04059f2d. Desktop images are matching 460×844 crops of a 1440×900 viewport; phone images are full 390×844 captures.

Surface	Before	After
Desktop project menu
Phone project menu

BB-Thread-ID: thr_ccffp4w2p2

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