Add Thread Organizer example plugin

[brsbl]

What was wrong

The repository had no complete reference consumer for plugin-owned thread workflows, leaving native section icons/actions, runtime skill slots, protected unread routing, and durable ordering as disconnected primitives. The remembered default stage was also easy to mistake for a semantic classification; Inbox placement could be undone by read/unread churn; automation-origin roots were excluded; semantic phase changes did not keep titles current; the fullscreen action was too easy to trigger; and the settings description aligned its text box rather than the capital R ink edge to the rounded panel.

What changed

• Add the Thread Organizer example with configurable workflow stages, protected Inbox routing, remembered-stage placement, native section icons/actions, CLI phase changes, and agent instructions.
• Teach the organizer skill to re-evaluate at substantive task starts, resolved indirect kickoffs, scope changes, pre-implementation, implementation/validation transitions, failed validation, and handoff. The default/remembered stage is explicitly mechanical; update_plan does not move workflow stage, while bb organizer phase does.
• Keep Inbox placement latched through read and unread changes after a thread enters Inbox. Only renewed agent work clears the latch and returns the thread to its remembered stage.
• Include automation-origin root threads in organization.
• On genuine non-Inbox semantic stage transitions, start an invisible title-reassessment worker that keeps an accurate title or applies a succinct replacement after rechecking that the thread and transition are still current.
• Opt the example's fullscreen action into Core's Command/Ctrl-plus-click activation requirement.
• Inset the settings description by the shared rounded-lg radius token and hang Inter's measured capital-R sidebearing so the visible ink edge lands on the corner tangent without an arbitrary pixel nudge.
• Add the missing Turbo dependency from example typecheck to @get-bb/plugin-sdk#build:types.
• Preserve PluginAgentConfiguration.skills as string[]; keep experimental_skillSlots optional and experimental; leave the inherited PLUGIN_SDK_VERSION unchanged at 0.4.14; and keep the planned engines.bbPluginSdk >=0.4.11 floor isolated to this example. No SDK 0.4.10 artifact is vendored or relabeled.

Before — exact parent PR head 7f85d7d45

After — exact head bcb110e54

Exact-head settings evidence

Exact-head intentional activation evidence

Plain click leaves the full workflow visible:

Command/Ctrl activation focuses the chosen section:

How you verified

• Node v22.22.1 arm64 with Turbo: all 47 focused example tests pass across core guidance, server behavior, app registration, sidebar actions, and controller state.
• Turbo typecheck passes for bb-plugin-thread-organizer-example and upstream generation/build dependencies.
• Built the exact head with the local source CLI: pnpm bb plugin build examples/plugins/thread-organizer.
• Removed generated untracked examples/plugins/thread-organizer/types/ after the build and confirmed every product worktree is clean.
• Focused skill coverage includes an indirect “read this brief” implementation kickoff and a Building → Testing / Deploy transition.
• Fresh desktop lifecycle verification: Inbox → read stays Inbox → unread stays Inbox → agent active returns to Planning.
• git diff --check 7f85d7d45a392dde5cc4dbd282fe9976bbf7c303..bcb110e541fa206b6900fa7b9c70cc984f15416a.
• The exact parent/head visual pair used the same empty Thread Organizer QA project, / route, manual grouping mode, expanded first section, ready composer state, and 1093×768 native window bounds. The settings and activation captures also came only from exact-head desktop dev apps.

Fixes # — no linked issue.

BB-Thread-ID: thr_eibej5m9xw

AGENT GENERATED: by GPT-5.6-Sol