fix(components): complete stable control contracts

[pathscale]

ConnectionSettings can now reject an invalid application ID before persistence or reconnect, and complex UI families derive stable control IDs from a caller-owned root. ImmersiveLanding owns its navigation and optional consent/PWA controls as one inventory subtree, repeated prompt instances avoid global IDs, and Slider uses the base-content token for visible thumb contrast.

The ThemeColorPicker CSP probe now tests a standard style attribute across frames. It treats missing computed-style support as unknown instead of permanently disabling theme colors, while still detecting a real browser CSP denial. Its native fixture now verifies that selecting a swatch produces an opaque applied accent, rather than accepting selection state alone.

The harness adds direct invalid-ID/non-commit checks, forward and backward landing navigation, Slider contrast, and applied-accent paint outcomes. Public API and usage docs cover the new validation and stable-ID contracts.

Validation on 0b2f646:

• bun run qa:build: pass
• Native chuzz/ps-qa component sweep: 101/101 pages
• ThemeColorPicker focused native outcomes: 5/5, including direct applied-accent paint
• Chrome CSP probe: denied policy {first:true,second:false}; no policy {first:true,second:true}
• Strict landing inventory: 5/5 controls attributed, zero ID or outcome gaps
• Strict PWA and Firefox inventories: 3/3 each, zero gaps
• Bun tests: 321/321
• API contract: 187 components
• Package check: 1,004 files and all exports/README imports resolve
• Diff check: pass

Known repository baseline: bun run lint reports 138 existing Biome errors, and bun run format rewrites hundreds of unrelated files before failing to parse Tailwind's @theme syntax in src/index.css. Formatter-only churn was restored; this PR contains only its six CSP/harness files plus the previously reviewed component work.

The automated release workflow should derive 3.2.3 from these fix: commits after review and merge. No manual version bump or publish is included.