agency: --spawn-topic flag, in-place by default, persistent ✓ buttons

[MagMueller]

Three behavior changes from real-use feedback.

1. `--spawn-topic` opt-in (default = run in-place)

Was: every Yes-tap created a new forum topic. Cards posted inside an existing worker topic spawned more topics on Yes — recursive nesting.

Now: default is in-place dispatch in the same thread the card lives in. Pass `--spawn-topic` when you specifically want a fresh topic — primarily for the `/agency` loop's half-hourly cards (each cycle deserves its own thread). No auto-protection: an agent inside a worker topic can still set `--spawn-topic` to fork another topic; the flag is honored without override.

Schema: new `spawn_topic INTEGER NOT NULL DEFAULT 0` column on `suggestions`. Migration via `ALTER TABLE` with duplicate-column swallow in `init_schema`, so existing DBs upgrade idempotently on first `agency_db.conn()`.

2. Persistent ✓ buttons replace keyboard-strip + 🔥 reaction

Default kinds (Yes / Skip / Edit) used to strip the keyboard after a tap. That made every answered card visually identical to a fresh one — across a 30-card feed, "did I answer this one?" was unreadable. PR #102 added a 🔥 reaction as a workaround marker.

Now: the keyboard stays. `_agency_mark_picked` grows a `reset_others` flag — for default kinds it strips ✓ from every other button before marking the tapped one (only the latest pick is highlighted, user can re-tap to change their mind). Custom buttons keep additive behavior (multi-tap stacks for variant-pickers like "Send draft A" + "Send draft B").

Drops the `setMessageReaction` call from #102 — the ✓ on the button is the at-a-glance marker.

3. Docstring updates

`agency-report` docstring now describes the spawn semantics, image-is-optional rule, and the "variable expandable count" pattern. Local skill file (not in this repo) carries the longer guidance about smart button labels and the multi-variant pattern for high-uncertainty asks.

Test plan

• Smoke-test default in-place — agency-report (no --spawn-topic) → tap Yes → agent runs in the SAME thread, no new topic created
• Smoke-test --spawn-topic — agency-report --spawn-topic → tap Yes → fresh forum topic spawns
• Persistent buttons — tap Yes, verify ✓ Yes shows; tap Skip, verify ✓ Skip shows + ✓ Yes cleared
• Custom buttons stay additive — tap Send A, then Send B → both show ✓

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Summary by cubic

Make topic spawning opt-in with --spawn-topic so Yes/Edit run in-place by default. Keep ✓ selections visible on buttons for quick at-a-glance state, and update docs for routing and image guidance.

• New Features

  • Add --spawn-topic to agency-report; default is in-place dispatch in the current thread. Use for /agency cycle cards or tasks that need their own topic.
  • Persist the inline keyboard. Default buttons (Yes/Skip/Edit) use exclusive ✓ highlighting; custom buttons stay additive so multiple picks can stack.
  • Remove the 🔥 reaction; the ✓ mark now shows the chosen action.
  • Docstring explains spawn semantics and when to skip images.

• Migration

  • Add spawn_topic INTEGER NOT NULL DEFAULT 0 to suggestions. Applied automatically in init_schema with idempotent ALTER TABLE. No manual steps.

^{Written for commit a0849cf. Summary will update on new commits.}