Remove dedicated toggle thinking button (#97)

## Summary
- Remove the standalone "Toggle thinking blocks" button from the session
header toolbar
- The block type filter dropdown already includes thinking as a
filterable block type, making the dedicated button redundant
- Remove the `t` keyboard shortcut, `toggleThinking()` method,
`showThinking` getter, and associated tests

## Test plan
- [ ] Verify thinking blocks can still be toggled via the block filter
dropdown
- [ ] Verify the `t` key no longer has any effect
- [ ] All 574 frontend tests pass

🤖 Generated with [Claude Code](https://claude.com/claude-code)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: userFRM

frontend/e2e/message-content.spec.ts

@@ -224,8 +224,14 @@ test.describe("Mixed content rendering", () => {
     const sid = await selectSession(page, project, count);
     await expectSessionLoaded(page, sid, displayRows);
 
-    // Toggle thinking off with keyboard shortcut
-    await page.keyboard.press("t");
+    // Open block filter dropdown and toggle thinking off
+    await page
+      .locator('button[aria-label="Filter block types"]')
+      .click();
+    await page
+      .locator(".block-filter-item")
+      .filter({ hasText: "Thinking blocks" })
+      .click();
 
     // Thinking blocks should be hidden
     const thinkingBlocks = page.locator(".thinking-block");

frontend/src/lib/components/layout/AppHeader.svelte

@@ -135,18 +135,6 @@
 
   <div class="header-right">
     {#if hasActiveSession}
-      <button
-        class="header-btn"
-        class:active={ui.isBlockVisible("thinking")}
-        onclick={() => ui.toggleThinking()}
-        title="Toggle thinking blocks (t)"
-        aria-label="Toggle thinking blocks"
-      >
-        <svg width="14" height="14" viewBox="0 0 16 16" fill="currentColor">
-          <path d="M8 1a7 7 0 100 14A7 7 0 008 1zm0 1.5a5.5 5.5 0 110 11 5.5 5.5 0 010-11zM8 4a.75.75 0 00-.75.75v3.5a.75.75 0 001.5 0v-3.5A.75.75 0 008 4zm0 6a.75.75 0 100 1.5.75.75 0 000-1.5z"/>
-        </svg>
-      </button>
-
       <div class="block-filter-wrap">
         <button
           class="header-btn"

frontend/src/lib/components/modals/ShortcutsModal.svelte

@@ -9,7 +9,6 @@
     { key: "]", action: "Next session" },
     { key: "[", action: "Previous session" },
     { key: "o", action: "Toggle sort order" },
-    { key: "t", action: "Toggle thinking blocks" },
     { key: "l", action: "Cycle message layout" },
     { key: "r", action: "Trigger sync" },
     { key: "s", action: "Star / unstar session" },

frontend/src/lib/stores/ui.svelte.ts

@@ -88,10 +88,6 @@ class UIStore {
   /** Set of block types currently visible. */
   visibleBlocks: Set<BlockType> = $state(readBlockFilters());
 
-  get showThinking(): boolean {
-    return this.visibleBlocks.has("thinking");
-  }
-
   constructor() {
     $effect.root(() => {
       $effect(() => {
@@ -140,10 +136,6 @@ class UIStore {
     this.theme = this.theme === "light" ? "dark" : "light";
   }
 
-  toggleThinking() {
-    this.toggleBlock("thinking");
-  }
-
   isBlockVisible(type: BlockType): boolean {
     return this.visibleBlocks.has(type);
   }

frontend/src/lib/stores/ui.test.ts

@@ -213,12 +213,6 @@ describe("UIStore", () => {
       expect(ui.theme).toBe("light");
     });
 
-    it("should toggle showThinking", () => {
-      const initial = ui.showThinking;
-      ui.toggleThinking();
-      expect(ui.showThinking).toBe(!initial);
-    });
-
     it("should toggle sortNewestFirst", () => {
       const initial = ui.sortNewestFirst;
       ui.toggleSort();
@@ -252,22 +246,6 @@ describe("UIStore", () => {
       expect(ui.hiddenBlockCount).toBe(0);
     });
 
-    it("should sync showThinking when toggling thinking block", () => {
-      ui.toggleBlock("thinking");
-      expect(ui.showThinking).toBe(false);
-
-      ui.toggleBlock("thinking");
-      expect(ui.showThinking).toBe(true);
-    });
-
-    it("should sync block filter when toggling thinking", () => {
-      ui.toggleThinking();
-      expect(ui.isBlockVisible("thinking")).toBe(false);
-
-      ui.toggleThinking();
-      expect(ui.isBlockVisible("thinking")).toBe(true);
-    });
-
     it("should reset all with showAllBlocks", () => {
       ui.toggleBlock("user");
       ui.toggleBlock("tool");

frontend/src/lib/utils/keyboard.test.ts

@@ -162,13 +162,6 @@ describe("registerShortcuts", () => {
       expect(navigateMessage).not.toHaveBeenCalled();
     });
 
-    it("should NOT trigger shortcut on Alt+T", () => {
-      const toggleSpy = vi.spyOn(ui, "toggleThinking");
-      fireKey("t", { altKey: true });
-      expect(toggleSpy).not.toHaveBeenCalled();
-      toggleSpy.mockRestore();
-    });
-
     it("should still navigate on plain J key", () => {
       fireKey("j");
       expect(navigateMessage).toHaveBeenCalledWith(1);

frontend/src/lib/utils/keyboard.ts

@@ -81,7 +81,6 @@ export function registerShortcuts(
         sessions.navigateSession(-1, filter);
       },
       o: () => ui.toggleSort(),
-      t: () => ui.toggleThinking(),
       l: () => ui.cycleLayout(),
       r: () => sync.triggerSync(() => sessions.load()),
       e: () => {