fix(site): require confirmation before executing terminal command from URL (#24650)

The terminal page auto-executed commands from the `?command=` query
parameter
on page load without user confirmation. Because session auth uses
`SameSite=Lax`
cookies, an attacker could craft a link (phishing email, Slack DM,
external page)
that executes arbitrary commands in a victim's workspace when clicked.

Adds a `ConfirmDialog` that shows the exact command and requires
explicit user
approval before it is passed to the terminal WebSocket. Canceling
removes the
`command` parameter from the URL and opens a plain terminal.

<details>
<summary>Implementation details</summary>

### Data flow (before)

`TerminalPage.tsx` reads `searchParams.get("command")` and passes it
directly
as `initialCommand` to `WorkspaceTerminal`, which embeds it in the
WebSocket
URL. `proxy.go` forwards it to the agent, which runs `bash -c
"<command>"`
immediately.

### Fix

- Added `commandConfirmed` state and `commandPendingConfirmation` flag
in
  `TerminalPage.tsx`.
- The `loading` prop passed to `WorkspaceTerminal` includes
`commandPendingConfirmation`, keeping the terminal in loading state
until
  the user confirms or cancels.
- The command is only passed as `initialCommand` after the user clicks
  "Run command" in the confirmation dialog.
- Trusted `?app=` commands (resolved from agent apps) bypass the dialog.
- Cancel removes the `?command=` parameter from the URL entirely.
- No backend changes needed; the frontend gates the command before it
  reaches the WebSocket.

### Terminal focus after dialog

`WorkspaceTerminal`'s autoFocus effect previously depended on
`[terminal, isVisible, autoFocus]` but not `loading`. It fired while the
Radix dialog's focus trap was active, so `terminal.focus()` was
intercepted. When `loading` became false after confirming the dialog,
the
effect did not re-fire. Fixed by adding `loading` to the effect deps and
skipping focus while `loading` is true.

### Files changed

| File | Change |
|------|--------|
| `site/src/pages/TerminalPage/TerminalPage.tsx` | Confirmation dialog,
`commandPendingConfirmation` in loading prop |
| `site/src/pages/TerminalPage/TerminalCommandConsentDialog.tsx` | New
dialog component |
| `site/src/pages/TerminalPage/TerminalCommandConsentDialog.stories.tsx`
| Storybook story for dialog |
| `site/src/pages/TerminalPage/TerminalPage.stories.tsx` |
`CommandConfirmation` story |
| `site/src/pages/TerminalPage/TerminalPage.test.tsx` | 4 new dialog
tests, `renderTerminalRaw` helper for non-blocking render |
| `site/src/modules/terminal/WorkspaceTerminal.tsx` | Add `loading` to
autoFocus effect deps |
| `site/e2e/helpers.ts` | Dismiss dialog in `openTerminalWindow` helper
|
| `site/e2e/tests/webTerminal.spec.ts` | Wait for
`data-status="connected"` + click terminal for focus |

</details>

> 🤖 Generated by Coder Agents

---------

Co-authored-by: Jakub Domeracki <jakub@coder.com>

site/e2e/tests/webTerminal.spec.ts

@@ -40,13 +40,16 @@ test("web terminal", async ({ context, page }) => {
 	const agent = await startAgent(page, token);
 	const terminal = await openTerminalWindow(page, context, workspaceName);
 
-	await terminal.waitForSelector("div.xterm-rows", {
+	await terminal.waitForSelector('[data-status="connected"]', {
 		state: "visible",
+		timeout: 30_000,
 	});
 
-	// Workaround: delay next steps as "div.xterm-rows" can be recreated/reattached
-	// after a couple of milliseconds.
-	await terminal.waitForTimeout(2000);
+	// Wait for xterm to render its row container and click to ensure
+	// the terminal has keyboard focus after the confirmation dialog.
+	const xtermRows = terminal.locator("div.xterm-rows");
+	await xtermRows.waitFor({ state: "visible" });
+	await xtermRows.click();
 
 	// Ensure that we can type in it
 	await terminal.keyboard.type("echo he${justabreak}llo123456");