Close the IDE with Cmd/Ctrl+E while the code editor has focus

[jadhavgaurav]

Description

This PR fixes Cmd/Ctrl+E so it closes the IDE while the Monaco editor has focus.

Two things were in the way:

1. Monaco owns Cmd+E for its actions.findWithSelection ("Use Selection for
   Find") command, so the keydown never reached the app's keyboard system.
   addKeyboardShortcutOverrides already re-dispatches Cmd/Ctrl+Enter,
   Cmd/Ctrl+Shift+Enter and Cmd/Ctrl+K on window; Cmd/Ctrl+E now joins them.
   Cmd/Ctrl+F is deliberately left to Monaco, so the find widget is still one
   keystroke away.
2. FullScreenIDE registered Escape, Control+e, Meta+e on a single handler
   that blurs Monaco when the editor has focus and only closes otherwise. Even
   with the key delivered, Cmd+E would have blurred instead of closing. The
   handler is now split: Escape keeps its step-out-then-close behaviour, and
   Mod+E always closes, mirroring the Mod+E that opened the IDE.

Closes #4959

Validation steps

1. Open a job in the IDE (Cmd+E from a selected job, or click the step).
2. Click into the code editor so Monaco has focus.
3. Press Cmd+E (Ctrl+E on Windows/Linux). The IDE closes.
4. Press Cmd+F with Monaco focused. Monaco's find widget still opens.
5. Press Escape with Monaco focused. Focus leaves the editor; a second Escape
   closes the IDE, as before.

Additional notes for the reviewer

1. New tests: assets/test/monaco/keyboard-overrides.test.ts covers the
   override registration and the dispatched event on both platforms, plus a
   guard that Mod+F is not claimed. FullScreenIDE.keyboard.test.tsx gains a
   "Mod+E - Close IDE" block. Five of these fail on main and pass here (I
   verified by reverting the two source files and re-running).
2. assets checks run locally: the new and changed files are Prettier-clean and
   add no new ESLint or tsc --project tsconfig.browser.json errors (both files
   already carry pre-existing errors; the counts are identical before and
   after). I could not run mix checks: there is no Elixir toolchain on this
   machine, and nothing in this change touches Elixir.
3. addKeyboardShortcutOverrides is also used by the manual run panel's custom
   dataclip editor, so Mod+E closes the IDE from there too. That seemed right;
   say the word if you'd rather scope it to the job editor.

AI Usage

Please disclose whether you've used AI anywhere in this PR (it's cool, we just
want to know!):

• I have used Claude Code
• I have used another model
• I have not used AI

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Pre-submission checklist

• I have performed an AI review of my code (we recommend using /review
  with Claude Code)
• I have implemented and tested all related authorization policies.
  (e.g., :owner, :admin, :editor, :viewer) — n/a, client-side
  keyboard handling only
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR