* fix(ui): make indexed access explicit across the Control UI
Burns down all 322 ui-lane noUncheckedIndexedAccess errors: untrusted
markdown/diff/patch parsing gets miss-tolerant guards (renderer rules
degrade to empty output instead of throwing mid-render), accumulators
use canonical sparse initialization, DOM lookups stay null-guarded, and
length-checked constructions carry named invariants.
* feat(tooling): enforce noUncheckedIndexedAccess in the core and ui lanes
Flips the flag on for tsconfig.core.json and tsconfig.ui.json (covering
src, all packages including the two deferred ones, and ui) and retires
the strict-ratchet lane wholesale: config, script, projects reference,
check/CI wiring, changed-lane routing, and sync test. The assertion-ban
oxlint override stays as an independent surface.
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