fix: detect clipped effort slider

[ventianima-lab]

Summary

• scope effort-slider discovery to the exact opened picker
• accept one attached ARIA slider in launcher-leased zero-viewport browser surfaces
• fail closed on ambiguous sliders and preserve bounded ARIA validation
• add production and capability-detection regressions

Verification

• focused Bun tests: 79 pass
• TypeScript: pass
• launcher tests: 196 pass, 1 platform skip
• dev-chat isolated: 9 pass
• remaining local suite: 368 pass; one unrelated environment-sensitive Windows install-location assertion sees the actual registered local launcher instead of its synthetic path
• full monolithic Bun run also reproduces a Bun 1.4.0 Windows segfault at dev-chat; isolated dev-chat passes

[ventianima-lab]

Reviewed exact head 6de4a84. Root cause is reproduced from the failed launcher trace: viewport 0x0, exactly two visible model radio rows, and one attached semantic effort slider at aria min=0 max=4 now=4. The patch scopes discovery to the exact opened picker, waits for attached state, requires exactly one slider, and keeps bounded ARIA and fail-closed selection checks. No prompt submission is part of this validation.