fix(cli): preserve media after the last transcript word

[user-github-me]

What

Preserve source media after the last transcript word when applying transcript cuts.

Why

On current main, removing a 0.5-second filler from a six-second source whose last word ends at four seconds produces only 3.5 seconds: the unrequested two-second outro is discarded. An explicit --keep 4-6 also fails with an empty cut list even though those seconds exist in the source.

Related work

#1973 introduced the transcript-cut workflow, and #4179 addressed audio splices and codec priming. This corrects the duration supplied to the existing cut-list compiler. Current issues and all 137 open PR file inventories were checked; no competing transcript-cut implementation was found.

How

Probe the input before compiling the cuts and pass its duration through the compiler's existing option. A --plan with --input uses the same source duration as encoding, so its ranges match the output. Transcript-only planning remains available without media tools and uses the last word's end; help and operations documentation explain the distinction.

Test plan

• Two command regressions fail on main with 15 controls passing: filler removal preserves the source tail, and an explicit keep range can select footage after the last word.
• All 17 focused cut-list, audio-splice and command tests pass. The new tests verify the plan, exact decoded PCM duration and audible output tail.
• Source and rebuilt packaged commands tested on a real six-second, 24fps video with a distinct two-second outro: removing the filler yields 132 frames / 5.5 seconds, and keeping the outro yields 48 frames / two seconds. Both retain the actual outro frame.
• Full CI skills discovery: 100 files, 878 passed, two skipped, zero failures, both in the workspace and in a clean archive without node_modules. Standalone import-boundary tests also pass.
• Fresh full workspace build, CLI rebuild, root lint, changed-file formatting/oxlint, test reachability and normal commit hooks pass.
• Fallow, comment-citation and comment-share checks pass; the generated skills manifest is in sync.