fix(ui): thread question_tx/plan_tx through 3 missed sites + passive close on tool-turnover

Two related UI/threading bugs surfaced during code review of 9475586.

## 1. Three missed build_agent sites in ui/mod.rs (companion to 9475586)

Last commit fixed the 9 build_agent calls in slash.rs but missed
three in ui/mod.rs that also passed `None, None` for question_tx +
plan_tx:

- L1770: `/cd` worktree-return to main repo
- L2507: `/model` switch rebuild
- L2764: auto worktree-cleanup return

Same C8-LSP shape: after any of these paths rebuilt the agent the
`question` + `plan_enter` + `plan_exit` tools silently disappeared
from the LLM's tool list for the rest of the session, because
`builder.rs:621` / `agent/builder.rs:252` install those tools only
when their channels are `Some`. The threading is now mechanical
across all 13 call sites (3 in main.rs, 9 in slash.rs, 4 in
ui/mod.rs — all `&Option<T>` refs auto-clone to `Option<T>` via
method resolution).

## 2. Chamber-abort false-positive on fresh ToolCall

`close_tool_chamber_if_open` aliases `close_tool_chamber_abort` for
back-compat (658a63e), which paints "⚠ tool denied · aborted · no
result" inside any chamber where `last_tool_name.is_some() ||
tool_chamber_open` at the time of close. The call at line 2123 fires
when a NEW ToolCall arrives over a chamber whose flags haven't
flipped yet — under parallel tool execution the next
`ToolExecutionStart` lands before the prior `ToolExecutionEnd`
processes, so EVERY in-flight chamber gets falsely branded as
"denied" while the tool is actually executing normally.

Switched 2123 to `close_tool_chamber_passive` — a fresh ToolCall is
chamber turnover, not a denial event. The other three abort callers
(`AgentEvent::Error` / `Interjected` / `ContextOverflow`) genuinely
are denial-shaped and stay on the abort variant.

This unmasks a separate underlying bug: the UI's single-chamber
state model (`tool_chamber_open: bool`, `last_tool_name: Option`)
can't represent multiple in-flight tool calls. Empty Read chambers
+ out-of-place `↳ trailers` for tools whose results arrive after a
newer call's chamber opens are the new visible symptom. A per-id
chamber state rework is filed separately.

Tests: existing `close_tool_chamber_*` unit tests still pass
(passive variant has equivalent gating behavior, just different
inner-row content).

Author: Yogthos

src/ui/mod.rs

@@ -1774,8 +1774,8 @@ pub async fn run_interactive(
                                                 context,
                                                 permission.clone(),
                                                 ask_tx.clone(),
-                                                None,
-                                                None,
+                                                question_tx.clone(),
+                                                plan_tx.clone(),
                                                 bg_store.clone(),
                                                                                                 #[cfg(feature = "lsp")]
                                                                                                 lsp_manager.clone(),
@@ -2120,7 +2120,21 @@ pub async fn run_interactive(
                         // it before opening the new one. Without this
                         // the new `╭─ NAME ─ args` lands inside the
                         // stale chamber.
-                        close_tool_chamber_if_open(&mut renderer, &mut last_tool_name, &mut tool_chamber_open)?;
+                        //
+                        // Use PASSIVE close, not abort. A new ToolCall
+                        // arriving over a stale chamber is chamber
+                        // turnover, not a denial event — the prior
+                        // tool may have finished cleanly and just
+                        // not flipped the flags yet (race, or a code
+                        // path that emitted ToolCall before the
+                        // previous ToolResult landed). Painting
+                        // "⚠ tool denied · aborted · no result" on it
+                        // would falsely brand a healthy tool call as
+                        // refused. The other three abort callers
+                        // (Error / Interjected / ContextOverflow) are
+                        // genuine denial-shaped events and stay on
+                        // `close_tool_chamber_if_open`.
+                        close_tool_chamber_passive(&mut renderer, &mut last_tool_name, &mut tool_chamber_open)?;
                         last_tool_name = Some(name.to_string());
                         if agent_line_started {
                             renderer.write_line("", Color::White)?;
@@ -2511,8 +2525,8 @@ pub async fn run_interactive(
                                         context,
                                         permission.clone(),
                                         ask_tx.clone(),
-                                        None,
-                                        None,
+                                        question_tx.clone(),
+                                        plan_tx.clone(),
                                         bg_store.clone(),
                                         #[cfg(feature = "lsp")]
                                         lsp_manager.clone(),
@@ -2768,8 +2782,8 @@ pub async fn run_interactive(
                                         context,
                                         permission.clone(),
                                         ask_tx.clone(),
-                                        None,
-                                        None,
+                                        question_tx.clone(),
+                                        plan_tx.clone(),
                                         bg_store.clone(),
                                                                                 #[cfg(feature = "lsp")]
                                                                                 lsp_manager.clone(),