fix: isolate debug storage quota failures for v1.9.2

[weidonglang]

Summary

• cap persisted Debug history at 200 entries and 256 KiB
• compact oversized legacy payloads and fall back to memory when storage is full or unavailable
• prevent Debug persistence failures from rejecting successful Tauri invokes or page navigation
• add quota-focused frontend acceptance and real isolated Tauri regression evidence
• prepare reviewed v1.9.2 NSIS/MSI metadata and update manifests

Verification

• Rust: 230 passed; Clippy passed
• Frontend build: 113 modules
• Frontend acceptance: 268 selectors plus Debug quota regression
• Feature acceptance: 300 total, 254 passed, 0 failed, 40 safe skips, 6 manual/policy
• Contract, drift, hygiene, safety, localization, and release consistency checks passed
• Real Tauri: 2,446,461-character legacy Debug history compacted below 256 KiB; Runtime/Environment navigation completed with no quota or business failures

Release boundary

This frontend-only hotfix does not change installer lifecycle, configuration migration, privileged operations, or system mutation contracts. Final assets were built once from product source commit bfa7b3c. Full evidence is in docs/release-v1.9.2.md.