test(config): measure what the page terminal costs the session route's closure

The session route is not served on the page until C7.7, but the closure the bundler
would walk is the same one and the terminal is the largest thing in it. Measured
against this branch's base, `ota-c7-1-terminal-document` at 51ae7b1b03:

  modules         4316 -> 4363        (+47)
  local modules    927 ->  971        (+44)
  minified bytes   3,930,787 -> 3,883,532   (-47,255)

The route gets smaller. It sheds six modules — the native component, the 612 KiB
engine string, the 105 KiB generated document script, the HTML module and the shell
and close around it — all string literals of a program the page cannot run, and gains
fifty: the component, its mount, the stylesheet and markup modules, the two the
controller split made, and the document's own thirty-nine, with xterm and the two
addons behind them at 607,945 bytes minified ESM on their own. `document-terminal-shape.ts`
is not among them: it declares types and esbuild emits nothing for it.

The census pins the trade in both directions, because "the engine string is absent"
passes just as well on a closure that resolved nothing: the six shed modules are
asserted gone, the eight gained ones and the three xterm packages asserted present,
and the document asserted whole except `message-bridge`, which ruling 19 keeps off the
page. It also holds the 16 px seam where C7.2 found it — nine offenders, no unresolved
styles — since the terminal's modules joining this closure is exactly the change that
could add a tenth unread.

The page-closure families were run before and after on the full corpus, never a
filtered scenarios file. Both sides: 7 files, 879 tests, exit 0 — and those 879
include the four page-closure pins, which assert the verdict of every golden C1, C2,
C3 and C5 record, so an unchanged run is an unchanged verdict table rather than an
unmeasured one. Per family with `vitest -t "session.terminal"`, both sides 19 passed
and 773 skipped. No family moved, which is what an inert lane should show: this
branch changes no RPC, no opcode, no grant and nothing the recorder reads.

Claude-Session: https://claude.ai/code/session_01JNnE9qzUZMMnqpZWCqM3nb

config/scripts/mobile-web-app-session-terminal-closure.test.mjs

@@ -0,0 +1,104 @@
+import { join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+import { describe, expect, it } from 'vitest'
+import { mobileWebAppRouteClosure } from './build-mobile-web-app-bundle.mjs'
+import { mobileWebAppDependenciesPresent } from './mobile-web-app-bundle-dependencies.mjs'
+import {
+  textInputFontSizeOffenders,
+  unresolvedTextInputStyles
+} from './mobile-web-app-text-input-font-size-seam.mjs'
+
+/**
+ * What putting the terminal on the page costs the session route's closure.
+ *
+ * The route is not served on the page until C7.7 — its module is still the native switch and
+ * there is no `.web.tsx` beside it — but the closure the bundler would walk is the same one, and
+ * the terminal is by far the largest thing in it. Measured here so the trade is a number rather
+ * than a claim, and so that a later change cannot quietly put the engine string back.
+ *
+ * Measured against `ota-c7-1-terminal-document` at 51ae7b1b03, which is this branch's base:
+ *
+ *   modules        4316 -> 4363   (+47)
+ *   local modules   927 ->  971   (+44)
+ *   minified bytes  3,930,787 -> 3,883,532   (-47,255)
+ *
+ * The route gets smaller. It sheds the 612 KiB engine string and the 105 KiB generated document
+ * script, both string literals it could not run, and gains xterm and the two addons as real code
+ * — 607,945 bytes minified ESM on their own — plus the document's own modules.
+ */
+
+const projectDir = fileURLToPath(new URL('../..', import.meta.url))
+const mobileDir = join(projectDir, 'mobile')
+
+const SESSION_ROUTE = 'app/h/[hostId]/session/[worktreeId].tsx'
+
+/** Gone with the WebView: string literals of a program the page has no way to run. */
+const SHED = [
+  'src/terminal/TerminalWebView.tsx',
+  'src/terminal/terminal-webview-engine.generated.ts',
+  'src/terminal/terminal-webview-document-script.generated.ts',
+  'src/terminal/terminal-webview-html.ts',
+  'src/terminal/terminal-webview-html/document-shell.ts',
+  'src/terminal/terminal-webview-html/document-close.ts'
+]
+
+/** The component, its mount, the stylesheet and the markup, and the two modules the split made. */
+const GAINED_OUTSIDE_THE_DOCUMENT = [
+  'src/terminal/TerminalWebView.web.tsx',
+  'src/terminal/terminal-web-document-mount.ts',
+  'src/terminal/terminal-webview-engine-css.generated.ts',
+  'src/terminal/terminal-webview-html.web.ts',
+  'src/terminal/terminal-webview-html/document-markup.ts',
+  'src/terminal/terminal-webview-html/document-style.ts',
+  'src/terminal/terminal-webview-ready-promises.ts',
+  'src/terminal/use-terminal-webview-controller.ts'
+]
+
+const XTERM_PACKAGES = ['@xterm/xterm', '@xterm/addon-unicode11', '@xterm/addon-webgl']
+
+/**
+ * The 16 px seam's verdict for this route, which C7.5 must leave exactly where C7.2 found it.
+ *
+ * Nine inputs under the floor is design §3's own count, and moving them is C7.2's work, not this
+ * lane's. It is asserted rather than left unmeasured because the terminal's own modules joining
+ * the closure is precisely the kind of change that could add a tenth without anyone looking.
+ */
+const EXPECTED_OFFENDERS = 9
+
+const bundles = mobileWebAppDependenciesPresent()
+const describeClosure = bundles ? describe : describe.skip
+
+describeClosure(
+  "the session route's page closure with the terminal on it",
+  () => {
+    it('gains the document, xterm and the addons, and sheds the engine string', async () => {
+      const { local, modules } = await mobileWebAppRouteClosure(SESSION_ROUTE)
+      for (const gone of SHED) {
+        expect(local, `${gone} is still in the closure`).not.toContain(gone)
+      }
+      for (const gained of GAINED_OUTSIDE_THE_DOCUMENT) {
+        expect(local, `${gained} is not in the closure`).toContain(gained)
+      }
+      for (const name of XTERM_PACKAGES) {
+        expect(
+          modules.some((module) => module.includes(`node_modules/${name}/`)),
+          `${name} is not in the closure`
+        ).toBe(true)
+      }
+      // The document, whole: every module the generator emits except the bridge, which ruling 19
+      // keeps off the page because those `message` frames belong to the shell.
+      const documentModules = local.filter((module) => module.startsWith('src/terminal/document/'))
+      expect(documentModules.length).toBeGreaterThanOrEqual(36)
+      expect(documentModules).not.toContain('src/terminal/document/message-bridge.ts')
+      expect(documentModules).toContain('src/terminal/document/page-document-modules.ts')
+    }, 300_000)
+
+    it('leaves the 16px seam census exactly where C7.2 found it', async () => {
+      const closure = await mobileWebAppRouteClosure(SESSION_ROUTE)
+      // Unresolved first: an offender count means nothing if the walk read no styles.
+      expect(unresolvedTextInputStyles(mobileDir, closure)).toEqual([])
+      expect(textInputFontSizeOffenders(mobileDir, closure)).toHaveLength(EXPECTED_OFFENDERS)
+    }, 300_000)
+  },
+  900_000
+)