fix(cli): preserve caption text inside script blocks

[user-github-me]

Importing caption text containing </script> through hyperframes transcribe can close the destination script and turn part of the caption into HTML. Replacement-string sequences such as $& and $$ also change the text or word IDs during insertion.

Escape < after JSON serialization and insert the serialized data through a replacement callback. This applies Studio's existing script-data convention to the CLI patcher and preserves literal caption text, IDs and timing for both supported variable names.

Validation:

• Five fail-first failures; nine regressions cover closing-tag forms, escaped script state, dollar sequences, quotes, backslashes and Unicode.
• All 223 transcription tests pass (one existing skip).
• Built CLI plus Chromium preserves text and IDs across 18 cases; repeated imports are byte-stable and input files remain unchanged.
• All 18 composition fixtures pass lint and strict browser check, with 9 layout and 5 contrast samples each.
• CLI build/typecheck, repository lint, formatting, commit hooks, comment checks, deletion and test-reachability checks pass.

This follows the generator fix in #3847. Transcript array-boundary parsing in #3896 remains separate.

[jrusso1020]

Two real escaping gaps in the caption patcher. A literal </script> in word text closes the host script, and $&, $' or $$ in the text are expanded by String.replace. Escaping < matches what Studio's caption generator already does, and the replacement callback removes the dollar-pattern expansion. The tests fail on main and pass here. Please land this before or together with #5236, which makes a decoded < reachable from VTT imports.

— Rames