Links in the terminal are highlighted, in a colour that adapts to the theme (#10)

[Maxaubert]

Closes #10.

What it does

A URL printed in the terminal is highlighted all the time, not only while the pointer is on it: the link colour, plus a faint underline. A click still opens it (that part was already there).

The colour

Blue by default (LINK_BLUE, #4ea1ff), moved only as far as the ground needs to reach 4.5:1:

• on a dark ground it is that blue as it is;
• on a light ground it is walked darker and stays a blue (GitHub light: rgb(52,106,168) at 5.1:1, measured on the page);
• on a ground that is itself blue, where a blue link is exactly what gets hard to see, it is walked until it reads;
• it is measured against the theme in force, so a custom background gets the same treatment, and it is recomputed when the theme changes.
  The underline is there for the last case: on a theme where the colour has to move close to the text's, a link is still told apart.

How

• lib/termLinks.ts (pure, tested): findLinks and linkColor. A sentence's full stop or comma, and a closing bracket the link never opened, are given back to the sentence, so (https://a.io/x). is a link in brackets while .../Prism_(optics) keeps its own.
• lib/termLinkPaint.ts: an xterm DECORATION per row a link sits on (foreground colour + an underline element with pointer-events: none). Scrollback is immutable, so its links are painted once and ride a marker; the live screen is redrawn in place by TUIs, so each pass repaints from the last finished line down, which is what keeps a rewritten row from carrying a stale blue run. Rebuilt on a resize (reflow) and a theme change; off on the alternate screen. Columns are counted in cells, since a wide character is one character and two cells.

Verification

• npm test: 355 pass (48 new). linkColor clears 4.5:1 on all 39 presets' own grounds, on four blue grounds, and on a non-hex ground.
• New e2e scenario links, reading computed colours off the page: a printed link wears the blue; the sentence's full stop does not; a 280-character link that wraps is painted on every row; switching to a light theme gives another colour that reads there and is still a blue.
• npm run typecheck: clean. npm run lint: 0 errors. npm run e2e: 12 scenarios pass.
• Looked at on the Pitch (black) theme and on Denim (navy).
• Packaged and installed on this machine; exe timestamp polled (08:15:10 -> 08:40:50), app relaunched.

Notes

• http and https only, the same links the click handler opens.
• Unsigned. Version stays 0.1.0 (nothing released yet).

🤖 Generated with Claude Code