paint recursion overflows stack on deep DOM

[XDLCS]

Steps to reproduce

Generate a page with 1272 nested <div>s and capture a screenshot with layout enabled:

n = 1272
html = '<div>' * n + 'x' + '</div>' * n
# serve it, then:
# moli fetch --layout --dump screenshot http://.../deep.html

Expected

A screenshot renders (Chrome 154 handles 5000 nesting levels fine).

Actual

thread 'render_runtime' has overflowed its stack
fatal runtime error: stack overflow, aborting

Process aborts with SIGABRT (rc=134).

Threshold (binary-searched)

nesting levels	result
1271	ok (rc=0)
1272	SIGABRT (rc=134)

The threshold is identical on 1.1.9 (a54ba82) — not fixed, not regressed. Per-frame stack cost is ~6.7 KB against the 8 MiB render_runtime stack. --dump json / markdown paths are unaffected (no layout pass).

Suggestion

Iterativize the layout/paint recursion (explicit work queue instead of mutual recursion through compute_child_layout), or grow the render thread stack.

Environment

• moli 1.1.10 (9b2f86b), Linux, --layout --dump screenshot

[BibekPathak]

@ldm0 this one too!!