0.4.0: collapse across a wrapping container, in all seven implementations

[ralyodio]

Follow-up to #83, which landed the first half. This is the rest.

What #83 left unfinished

#83 closed the gaps so every seam could touch. But the panels then touched while still drawing two borders, because a seam merges only where two bordered siblings meet — and the only way to put a stack of panels beside one tall panel is to wrap the stack in a column, which is not itself bordered. So the seam down the middle of every screen was the one seam that could never merge, and a grid never merged at all. The dashboard looked right only because its panels happen to be direct children of the row.

before                                after
╭─ Services ─╮╭─ Kernel ─────╮        ╭─ Services ─┬─ Kernel ─────╮
│ ...        ││ ...          │        │ ...        │ ...          │
╰────────────╯╰──────────────╯        ╰────────────┴──────────────╯

Containers now take a bordered flag saying their own edges are panel borders, and a grid of panels merges its tracks. It is declared rather than inferred: the children are built only once the layout has been solved, and the seam has to be known before that, so there is nothing to inspect at the moment the question is asked.

And panels with a background

box filled its whole rect before drawing its border, which erased the neighbour's border out of the shared column — so the merge found a blank cell and overwrote it, leaving a corner where a junction belonged. That is why the themes grid showed ╭ where a ┬ was due. Filling under collapsing now stops at the border ring, which the border then paints in the same background.

All seven implementations

TypeScript, Rust, Go, Python, Zig and C/C++, plus the Ruby/PHP/Perl bindings that ride on the C++ demo.

• Rust and Zig widened their grid gap arithmetic to signed, since a merged track seam is minus one.
• In C++ the flag has to be copied into the panel body: those lambdas are stored and run by flush() after the enclosing function returns, so a captured-by-reference gap was a dangling local — which is exactly how the dashboard's sub-panels kept their gap while everything around them merged.

Uncollapsed rendering is untouched

The regenerated demo-parity.json proves it: of 240 cases, all 120 open frames are byte-identical, and 90 of the 120 collapsed ones changed.

0.4.0

The demo has to move with the library rather than after it: it calls worldMap, which does not exist in the published 0.3.0, so a demo published against ^0.3.0 would resolve the old library and crash on the world screen.

Checks

• TypeScript: 356 tests, under both bun test and node --test
• Go: all suites; Python: 36 tests; Rust: 17 demo-parity; Zig: 17; C++: 9/9 including its own 240-case parity
• Ruby and Perl bindings: each reports 240 exact reference frames in both border modes (PHP's extension needs phpize, built in CI)
• Rendering all eleven screens both ways and counting seams that stayed open gives zero on every one
• bun install --frozen-lockfile clean; node apps/demo/bin/hqtui-demo.mjs --version prints hqtui-demo 0.4.0

🤖 Generated with Claude Code

https://claude.ai/code/session_01VhrgsHr1C5BYxXDpN1mahf