Add interactive choice-picker menus for finite-choice slash commands

Slash commands with a finite set of options (/reasoning, /fast, ...) now
render a tappable card with buttons (2 per row, ✓ on the current value)
instead of a plain text status card. The mechanism is generic: any command
that calls the adapter's send_choice_picker() gets a picker automatically.

Wire protocol (docs/04, frames.schema.json):
- picker.choice (server→app): {picker_id, title, choices[]}
- picker.select (app→server): {picker_id, value}
- pickers capability flag now True in server_caps

gateway-plugin:
- protocol.py: picker.choice/picker.select frame types + picker_choice()
- dispatch.py: route picker.select → adapter.on_picker_select
- adapter.py: send_choice_picker() (fails cleanly with no live device so
  hermes falls back to text), on_picker_select(), in-memory pending pickers
  (gateway restart expires them; stale select is a no-op), pickers=True

app (KMP):
- Protocol.kt: PickerChoice/PickerChoicePayload + pickerSelectFrame()
- ChatStore.kt: PickerItem + onPickerChoice (idempotent) + resolvePicker
  (optimistic, one-shot)
- ChatDb.kt: persist PickerItem in the messages table (polymorphic decode)
- IrisController.kt: picker.choice routing + selectPicker() action
- ChatScreen.kt: PickerCard composable (locks after selection)

Tests:
- python: 3 picker tests (roundtrip, no-device fallback, stale-select noop)
- kotlin: ChatStorePickerTest (add/idempotent/resolve/one-shot/noop/serialize)
- fixture fix: clear leaked IRIS_HTTP_PORT/IRIS_WS_HOST env so the adapter
  binds the ephemeral port (a prior test's interactive_setup() polluted the
  process env, colliding with a live gateway on 8791)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

docs/protocol/frames.schema.json

@@ -66,7 +66,8 @@
       "history": { "description": "Paged full message history for a chat/thread (response to a history request). Reconstructed from the outbox log; used to populate the view on first open / after a process death, since sync only replays the outbox delta.", "payload": { "messages": { "type": "array", "items": { "type": "object", "properties": { "message_id": {"type":"string"}, "role": {"type":"string","enum":["user","assistant"]}, "text": {"type":"string"}, "reasoning": {"type":"string"}, "model": {"type":"string"}, "tokens": {"type":"integer"}, "runtime": {"$ref":"#/definitions/runtime"}, "ts": {"type":"integer"}, "media": {"type":"array","items":{"$ref":"#/definitions/media_ref"}} } } }, "has_more": { "type": "boolean", "description": "True when older pages exist." }, "oldest_message_id": { "type": "string", "description": "before_message_id for the next (older) page." } } },
       "media.pull.end": { "payload": { "ok": { "type": "boolean" } } },
       "media.upload.ack": { "description": "Response to media.upload.end; ref is cached and usable in message.send media_refs.", "payload": { "ok": { "type": "boolean" }, "media_ref": { "type": "string" } } },
-      "commands.catalog": { "description": "Response to a commands.catalog request: the gateway's slash-command catalog for the app's '/' drawer. Derived from hermes' COMMAND_REGISTRY (gateway-available subset) plus plugin-registered commands. The app fuzzy-matches the typed prefix client-side.", "payload": { "commands": { "type": "array", "items": { "type": "object", "properties": { "name": { "type": "string", "description": "Canonical command with leading slash, e.g. \"/new\"." }, "description": { "type": "string" }, "args_hint": { "type": "string", "description": "Argument placeholder, e.g. \"[name]\"; empty when none." }, "category": { "type": "string", "description": "Registry category (Session, Configuration, Tools & Skills, Info, Exit, Plugin)." }, "aliases": { "type": "array", "items": { "type": "string" }, "description": "Alternative names with leading slash, e.g. [\"/reset\"] for /new." } } } } } }
+      "commands.catalog": { "description": "Response to a commands.catalog request: the gateway's slash-command catalog for the app's '/' drawer. Derived from hermes' COMMAND_REGISTRY (gateway-available subset) plus plugin-registered commands. The app fuzzy-matches the typed prefix client-side.", "payload": { "commands": { "type": "array", "items": { "type": "object", "properties": { "name": { "type": "string", "description": "Canonical command with leading slash, e.g. \"/new\"." }, "description": { "type": "string" }, "args_hint": { "type": "string", "description": "Argument placeholder, e.g. \"[name]\"; empty when none." }, "category": { "type": "string", "description": "Registry category (Session, Configuration, Tools & Skills, Info, Exit, Plugin)." }, "aliases": { "type": "array", "items": { "type": "string" }, "description": "Alternative names with leading slash, e.g. [\"/reset\"] for /new." } } } } } },
+      "picker.choice": { "description": "Interactive choice picker (one tap -> one value) for finite-choice slash commands (/reasoning, /fast, ...). The app renders the title + choice buttons and answers with picker.select carrying the same picker_id. Outboxed, so a reconnecting device re-renders a still-pending picker; pending state is in-memory only (a gateway restart expires it).", "payload": { "picker_id": { "type": "string" }, "title": { "type": "string" }, "choices": { "type": "array", "items": { "type": "object", "properties": { "value": { "type": "string" }, "label": { "type": "string" }, "is_current": { "type": "boolean" } } } } } }
     },
     "app_to_server": {
       "hello": { "description": "First frame; auth + caps.", "payload": { "token": { "type": "string" }, "device_id": { "type": "string" }, "device_name": { "type": "string" }, "caps": { "type": "object", "properties": { "min_protocol": {"type":"integer"}, "media": {"type":"boolean"}, "push": {"type":"string"} } }, "fcm_token": { "type": "string" }, "ntfy_topic": { "type": "string" } } },
@@ -88,6 +89,7 @@
       "history": { "description": "Load a page of full message history for a chat/thread (initial open, scroll-up pagination).", "payload": { "before_message_id": { "type": "string", "description": "Return messages older than this (omit for newest page)." }, "limit": { "type": "integer", "description": "Max messages (default 50, max 200)." } } },
       "message.delete": { "description": "Completely delete the given message(s) from a chat/thread. The server removes them from the outbox (so history/sync no longer return them) and from the hermes session store (so no search trace survives and they are not recoverable), then broadcasts message.deleted to every device. Idempotent: a message already gone (pruned) still yields a message.deleted broadcast.", "payload": { "message_ids": { "type": "array", "items": { "type": "string" }, "description": "One or more message_id values to delete." } } },
       "fcm.register": { "payload": { "fcm_token": { "type": "string" }, "ntfy_topic": { "type": "string" } } },
+      "picker.select": { "description": "Answer an interactive picker (picker.choice). The server runs the command's selection callback and delivers its reply as a normal message in the picker's chat. Unknown/expired picker ids are a no-op.", "payload": { "picker_id": { "type": "string" }, "value": { "type": "string" } } },
       "ping": { "payload": { "ts": { "type": "integer" } } }
     }
   },
@@ -99,11 +101,9 @@
   },
   "x-planned-frames": [
     { "name": "picker.model", "direction": "server_to_app", "note": "Model/provider picker prompt. Planned, not implemented." },
-    { "name": "picker.choice", "direction": "server_to_app", "note": "Generic choice picker prompt. Planned, not implemented." },
     { "name": "picker.clarify", "direction": "server_to_app", "note": "Clarify picker prompt. Planned, not implemented (clarifies arrive as notification + message)." },
     { "name": "picker.approval", "direction": "server_to_app", "note": "Approval picker prompt. Planned, not implemented (approvals arrive as notification)." },
     { "name": "picker.confirm", "direction": "server_to_app", "note": "Confirmation picker prompt. Planned, not implemented." },
-    { "name": "picker.select", "direction": "app_to_server", "note": "Picker answer. Planned, not implemented." },
     { "name": "commands.complete", "direction": "server_to_app", "note": "Slash-command autocomplete. Planned, not implemented (the app fuzzy-matches the commands.catalog list client-side)." },
     { "name": "commands.complete", "direction": "app_to_server", "note": "Slash-command autocomplete request. Planned, not implemented." },
     { "name": "agent.busy", "direction": "server_to_app", "note": "Agent-busy indicator. Planned, not implemented (typing frames cover it)." },