perf: cut cold-start download 58% and startup heap 22% via measured chunk-graph fixes (#2742)

* fix(ui): update session-switch-resync test to current handleEvent/setSessionTodos signatures

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* perf(build): split Shiki grammars/themes, CodeMirror legacy modes, and @pierre/diffs into on-demand chunks

Merging @shikijs/langs into one manual vendor chunk made the first language
request download every grammar (7.4 MB raw / 1 MB gzip). Letting Rollup split
these packages per dynamically imported module downloads only the languages,
themes, and modes actually used — matching how the worker build already
behaves. @pierre/diffs is split the same way so its pure patch parser (used by
the eager tool renderer) no longer drags the Shiki-importing render stack into
the startup graph.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* perf(ui): restore lazy heavy views and stop eager settings-graph loading

- MainLayout: DiffView/FilesView/GitView/PlanView return to lazyWithChunkRecovery
  (they were silently made static in 2031e3b4 while their Suspense wrappers
  remained), keeping the CodeMirror and @pierre/diffs stacks out of startup.
- ContextPanel: same lazy treatment for its Diff/Files/Git/Plan/Walkthrough
  tabs, with null Suspense fallbacks.
- CommandPalette imported getSettingsNavIcon from SettingsView, statically
  pulling the entire settings surface (SkillsPage -> CodeMirrorEditor -> vim
  mode, theme registry -> @pierre/diffs) into the eager graph; the helper now
  lives in lib/settings/metadata.
- The windowed SettingsWindow mounts only after its first open: rendering the
  lazy component closed made React fetch the SettingsView chunk graph at
  startup.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* perf(ui): keep @pierre/diffs + Shiki out of the eager chat graph and defer diff worker warmup

- DiffWorkerProvider no longer statically imports @pierre/diffs/worker or the
  theme registry, and no longer spawns 3 workers plus a main-thread shared
  highlighter during mount. Pools are created on demand through a dynamic
  module load, warmed via requestIdleCallback after startup settles, and
  useWorkerPool notifies consumers when a pool becomes available.
- ToolPart's rich diff preview moves to lazily loaded ToolPartDiffPreview;
  the plain-text patch (PlainDiffFallback) renders while the chunk loads,
  mirroring the existing error fallback. Theme registration happens during
  render inside the lazy module so PatchDiff never renders unregistered ids.
- ChatInput mounts its lazy ToolOutputDialog only after the first attachment
  preview opens instead of fetching the dialog chunk on the draft screen.
- getMarkdownSyntaxVars moves to a pierre-free markdownSyntaxVars module so
  eager code-rendering consumers stop importing the registration module.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* perf(web): load ghostty-web and Nerd Fonts on first terminal use

- ghostty-web (638 KB raw JS + WASM VT) is dynamically imported when a
  terminal actually mounts; TerminalView stays eagerly importable for the
  bottom dock.
- The ~2 MB of CDN Nerd Fonts are no longer preloaded and force-loaded on
  every cold start. index.html exposes an idempotent
  __openchamberEnsureNerdFonts hook; TerminalViewport requests it on mount
  and waits up to 2s so a cached font is in place before the glyph atlas is
  built, while a cold CDN fetch never blocks the terminal. Runtimes without
  the hook (VS Code, mobile) resolve immediately, matching their existing
  fallback-font behavior.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

---------

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/components/chat/markdown/markdownSyntaxVars.ts

@@ -0,0 +1,31 @@
+import type { Theme } from '@/types/theme';
+
+/**
+ * Build the `--md-syntax-*` CSS custom properties for the given app theme.
+ * Apply the result as inline styles on the markdown container so the static
+ * Shiki theme resolves to the active palette.
+ *
+ * Lives apart from `markdownTheme.ts` because that module imports
+ * `@pierre/diffs` for theme registration; eager consumers of these CSS vars
+ * (tool output, code blocks) must not pull that stack into the startup graph.
+ */
+export const getMarkdownSyntaxVars = (theme: Theme): Record<string, string> => {
+  const base = theme.colors.syntax.base;
+  const tokens = theme.colors.syntax.tokens ?? {};
+  const status = theme.colors.status;
+
+  return {
+    '--md-syntax-foreground': base.foreground,
+    '--md-syntax-comment': base.comment,
+    '--md-syntax-string': base.string,
+    '--md-syntax-number': base.number,
+    '--md-syntax-keyword': base.keyword,
+    '--md-syntax-operator': base.operator,
+    '--md-syntax-function': base.function,
+    '--md-syntax-type': base.type,
+    '--md-syntax-variable': base.variable,
+    '--md-syntax-property': tokens.variableProperty ?? base.variable,
+    '--md-syntax-inserted': status.success,
+    '--md-syntax-deleted': status.error,
+  };
+};

packages/ui/src/components/chat/markdown/markdownTheme.ts

@@ -1,5 +1,4 @@
 import { registerCustomTheme, type ThemeRegistrationResolved } from '@pierre/diffs';
-import type { Theme } from '@/types/theme';
 import { MARKDOWN_SHIKI_THEME, MARKDOWN_SHIKI_THEME_DEFINITION } from './markdownShikiThemeDefinition';
 
 // The static Shiki theme name. Its definition (token colors referencing
@@ -27,29 +26,3 @@ export const ensureMarkdownShikiTheme = (): void => {
     Promise.resolve(MARKDOWN_SHIKI_THEME_DEFINITION as unknown as ThemeRegistrationResolved),
   );
 };
-
-/**
- * Build the `--md-syntax-*` CSS custom properties for the given app theme.
- * Apply the result as inline styles on the markdown container so the static
- * Shiki theme resolves to the active palette.
- */
-export const getMarkdownSyntaxVars = (theme: Theme): Record<string, string> => {
-  const base = theme.colors.syntax.base;
-  const tokens = theme.colors.syntax.tokens ?? {};
-  const status = theme.colors.status;
-
-  return {
-    '--md-syntax-foreground': base.foreground,
-    '--md-syntax-comment': base.comment,
-    '--md-syntax-string': base.string,
-    '--md-syntax-number': base.number,
-    '--md-syntax-keyword': base.keyword,
-    '--md-syntax-operator': base.operator,
-    '--md-syntax-function': base.function,
-    '--md-syntax-type': base.type,
-    '--md-syntax-variable': base.variable,
-    '--md-syntax-property': tokens.variableProperty ?? base.variable,
-    '--md-syntax-inserted': status.success,
-    '--md-syntax-deleted': status.error,
-  };
-};