feat: copy selected text

[denolfe]

Dragging over text in the viewer now copies it to the clipboard when the mouse button is released. The status line reports the result.

Key Changes

• Copy on mouse release
  • The renderer emits a selection event once per finished drag. A handler in App copies the text and shows a Copied N chars status.
  • Empty and whitespace-only selections stay silent. A bare click finishes an empty selection, so it must not report anything.
• Clipboard path chosen once per session
  • resolveCopyStrategy prefers a local clipboard command: pbcopy, wl-copy, xclip, xsel, or clip.exe.
  • SSH sessions use OSC 52, an escape sequence that asks the terminal to set the clipboard. The Linux tools are also skipped when no display server is set, since they error or hang without one.
• Inline code copies clean
  • A codespan is padded with half-block cells that share a text renderable with the code itself. Those cells are stripped from the copied text.
  • A drag that catches only the padding counts as an empty selection.
• Themed selection highlight
  • Selections paint theme.selectionBg instead of reverse video. Text keeps its own foreground color.

Design Decisions

The clipboard path is resolved before the copy, not after a failure. tmux configured with set-clipboard external discards an application's OSC 52 request, and the OpenTUI call still reports success. A fallback triggered by failure would never fire, so a local command wins whenever the session is not remote.

The selection color is seeded on OpenTUI's shared text renderable base class rather than passed as a prop. OpenTUI exposes selectionBg per renderable with no app-wide default. The viewer mounts blocks progressively, so every current and future text element would otherwise have to carry the prop.

References / Links

• XTerm control sequences: defines the OSC 52 clipboard sequence.
• tmux manual: documents when set-clipboard forwards an application's clipboard request.

[github-actions]

Startup benchmark (--render test/exhaustive.md, linux-x64)

build	mean	ratio	verdict
baseline (main@beedc6d)	359.7ms ± 5.3ms	—
PR	364.5ms ± 9.2ms	1.01×	✅ ok

Thresholds: warn ≥ 1.1×, fail ≥ 1.25×. Baseline built from main.

First-frame (large.md, runs=10)

metric	baseline (main@beedc6d)	PR	ratio	verdict
first-frame	271.1ms	273.1ms	1.01×	✅ ok

Thresholds: warn ≥ 1.1×, fail ≥ 1.25×. Baseline built from main.

Scroll (large.md)

metric	baseline (main@beedc6d)	PR	ratio	verdict
full_mount	10248.0ms	10772.0ms	1.05×	✅ ok
step_p50	23.2ms	22.3ms	0.96×	✅ ok
step_search_p50	22.8ms	23.3ms	1.03×	✅ ok
stepMatch_p50	17.2ms	17.9ms	1.04×	✅ ok
commit	139.7ms	146.7ms	1.05×	✅ ok

Thresholds: warn ≥ 1.1×, fail ≥ 1.25×. Baseline built from main.