docs(specs): add TUI inline mention picker spec, relocate busy status to input separator

specs/011-tui/spec.md

@@ -16,6 +16,7 @@ related:
   - "[[007-channels/spec]]"
   - "[[026-tui-subagent-management/spec]]"
   - "[[030-tui-slash-autocomplete/spec]]"
+  - "[[084-tui-mention-picker/spec]]"
   - "[[068-session-persistence/spec]]"
 ---
 
@@ -63,15 +64,27 @@ TuiApp
 | SubAgents | `a` | Interactive subagent sidebar with j/k navigation and transcript viewer |
 | Fleet | `f` | Read-only table of all agent sessions (active/completed/unknown); auto-refreshed by `AgentEvent::FleetSnapshot` (#3884) |
 | Task Registry | `/tasks` | Live table of all supervised tasks (see below) |
-| Status Bar | always | Current operation spinner + short status text |
+| Input Separator | (above input) | Input prompt, busy spinner + verb (when busy), interrupt hint (#6649) |
+| Status Bar | always | Stable session parameters, streaming tok/s + TTFT, transient critical hints |
 
 Tab cycling order includes SubAgents. See `026-tui-subagent-management/spec.md` for full SubAgents panel spec.
 
 ## Spinner Rule (NON-NEGOTIABLE)
 
 **Every background or implicit operation must show a visible spinner with a short status message.**
 
-Examples:
+The spinner and verb are rendered in the **input separator row** (above the input composer), appended after the row's existing idle elements:
+```
+you ▸ {mode hint} {~N tokens} [queue badges] ▸▸▹ {verb} · {interrupt-hint}
+```
+
+Where:
+- `you ▸` — prompt glyph; mode hint, `~N tokens` context estimate, and queue badges are the row's existing elements, unchanged
+- `▸▸▹` — animated breeze spinner (constant 3-cell width; rendered as a static `·` when motion is off)
+- `{verb}` — humanized present-continuous status (e.g., `searching · memory`), truncated before the hint under width pressure
+- `{interrupt-hint}` — interrupt instruction; its key/text is owned by #6646 (`esc to interrupt` today, `ctrl+c` once #6646 lands)
+
+Examples of `{verb}`:
 - `Searching memory…`
 - `Executing tool: shell`
 - `Connecting to MCP server…`
@@ -80,6 +93,8 @@ Examples:
 
 Status messages: short, present continuous tense, no punctuation except `…`.
 
+**When idle** (no background operation), the separator row renders exactly as before this change: prompt glyph, mode hint, `~N tokens` estimate, and queue badges — no spinner, no verb, no interrupt hint. The bottom status bar no longer renders the busy spinner/verb segment in any state (#6649).
+
 ## TuiChannel Invariants
 
 - `TuiChannel` owns stdin/stdout — **mutually exclusive with ACP stdio transport**

specs/030-tui-slash-autocomplete/spec.md

@@ -160,7 +160,7 @@ THEN the dropdown is dismissed automatically
 | NFR-001 | Performance | Filter and re-render must complete within a single 16 ms frame; no async work is performed — all filtering is synchronous over the static registries |
 | NFR-002 | Correctness | Must not interfere with existing key bindings: Esc (→ Normal mode), Enter (→ submit), Up/Down (→ history navigation) are re-routed only while the dropdown is active |
 | NFR-003 | Correctness | Must not conflict with the existing Command Palette (`:` in Normal mode) — the two flows are mutually exclusive by construction (`command_palette` vs `slash_autocomplete` state fields) |
-| NFR-004 | Correctness | Must not conflict with the `@` file picker (`KeyCode::Char('@')` path in `handle_insert_key`) |
+| NFR-004 | Correctness | Must not conflict with the inline mention picker (`[[084-tui-mention-picker/spec]]`); both surfaces are non-modal overlays with distinct trigger rules (slash-autocomplete triggers on `/` at start of empty input; mention picker triggers on `@` at word-start) |
 | NFR-005 | Accessibility | The popup must be dismissible without accepting any suggestion at any point |
 | NFR-006 | Architecture | The autocomplete state must live in `App` as a dedicated field, not inside `CommandPaletteState` |
 | NFR-007 | Architecture | No new crate dependencies are permitted; ratatui `List` + `Clear` widgets (already used) are sufficient |