docs(openspec): backfill missing proposals

openspec/changes/improve-cross-platform-stability/design.md

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+## Context
+
+The stability of account injection and detection differs across platforms, with risks concentrated in:
+- DB lock conflicts causing unstable writes.
+- Version-detection failures causing incorrect injection-path routing.
+- Compatibility boundaries introduced by OS behavior differences.
+
+## Goals / Non-Goals
+
+- Goals:
+  - Improve cross-platform write and switching stability.
+  - Define clear priority between version detection and capability probing.
+  - Improve observability and troubleshooting efficiency.
+- Non-Goals:
+  - Extend support to non-default runtime configuration path parsing.
+  - Introduce new business strategies.
+
+## Decisions
+
+- Decision: Transactionalize the write flow to reduce partial-success risk.
+- Decision: Add DB busy retry and `busy_timeout`.
+- Decision: On version-detection failure, use `package.json` as Windows fallback source.
+- Decision: Give capability probing higher priority than version detection; prefer new format when a new-format key is detected.
+
+## Risks / Trade-offs
+
+- A stricter write flow may add minor latency.
+- Running capability probing and version detection together increases implementation complexity.
+
+## Migration Plan
+
+1. Complete transactional writes and retry mechanisms.
+2. Add version-detection cache and fallback.
+3. Introduce strategy-based injection and capability probing.
+4. Add corresponding tests and regression verification.

openspec/changes/improve-cross-platform-stability/proposal.md

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+# Change: Cross-Platform Stability and Robustness Improvements (P0+P1+P2)
+
+## Why
+
+- Account injection and detection across platforms are vulnerable to DB locks, version-detection failures, and OS-level differences.
+- Stability, diagnosability, and maintainability must improve without changing business semantics.
+
+## What Changes
+
+- Make the write flow atomic (transaction-wrapped).
+- Add DB lock retry and `busy_timeout`.
+- Add cache and lower-noise logging for version detection.
+- Add a more robust Windows fallback for version detection (read from `package.json`).
+- Introduce strategy-based injection routing (new/legacy/dual-write).
+- Add capability probing: prefer new format when new-format keys are detected.
+
+## Impact
+
+- Affected specs: `ide-auth-compat`
+- Affected code:
+  - `src/ipc/database/cloudHandler.ts`
+  - `src/ipc/database/handler.ts`
+  - `src/utils/antigravityVersion.ts`
+  - `src/utils/paths.ts` (this stage covers default runtime configuration path only)
+  - `src/types/db.ts`
+
+## Constraints
+
+- Do not change existing business semantics; only improve stability and structure.
+- This stage only covers the default runtime configuration path.
+
+## Risks
+
+- Transaction and retry logic may change when errors surface.
+- Capability probing may conflict with version detection unless priority is clearly defined.

openspec/changes/improve-cross-platform-stability/specs/ide-auth-compat/spec.md

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+## ADDED Requirements
+### Requirement: Atomic Injection Writes
+The system SHALL use transactions when writing IDE state to ensure atomic updates.
+
+#### Scenario: Injection write consistency
+- **WHEN** injecting new/legacy token formats
+- **THEN** related keys are committed in a single transaction to avoid partial writes
+
+### Requirement: DB Lock Retry
+The system SHALL perform short backoff retries on SQLITE_BUSY or SQLITE_LOCKED.
+
+#### Scenario: Successful DB lock retry
+- **WHEN** a write encounters a lock
+- **THEN** the system retries for a limited number of attempts and records logs
+
+### Requirement: Version Detection Cache
+The system SHALL cache IDE version-detection results in-process to reduce repeated system calls.
+
+#### Scenario: Version cache hit
+- **WHEN** IDE version is requested multiple times
+- **THEN** the system call is executed only once
+
+### Requirement: Windows Version Detection Fallback
+The system SHALL read `package.json` as a fallback source when Windows version detection fails.
+
+#### Scenario: Windows version detection failure
+- **WHEN** PowerShell fails to read version
+- **THEN** version is obtained by falling back to `package.json`
+
+### Requirement: Strategy-Based Injection
+The system SHALL use a strategy pattern to split new/legacy/dual-write injection paths for clearer structure.
+
+#### Scenario: Strategy selection
+- **WHEN** version-based and capability-based routing differ
+- **THEN** the system selects the corresponding injection implementation via strategy objects
+
+### Requirement: Prefer New Format via Capability Probing
+The system SHALL prefer new-format injection when new-format keys are detected.
+
+#### Scenario: New-format key exists
+- **WHEN** `antigravityUnifiedStateSync.oauthToken` exists
+- **THEN** injection uses new format with higher priority

openspec/changes/improve-cross-platform-stability/tasks.md

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+## 1. Scope and Planning Confirmation
+- [ ] 1.1 Review `proposal.md`.
+- [ ] 1.2 Finalize priority: capability probing vs version detection.
+- [ ] 1.3 Confirm this stage covers default runtime configuration path only.
+
+## 2. Implementation
+- [x] 2.1 Make write flow transactional (atomic).
+- [x] 2.2 Add DB lock retry and `busy_timeout`.
+- [x] 2.3 Add version-detection cache and lower-noise logs.
+- [x] 2.4 Add Windows fallback for version detection (`package.json`).
+- [x] 2.5 Split injection path by strategy pattern.
+- [x] 2.6 Add capability probing: prefer new format when new key is detected.
+
+## 3. Verification
+- [x] 3.1 Simulate SQLITE_BUSY/LOCKED retry behavior.
+- [x] 3.2 Verify fallback path for version-detection failure.
+- [x] 3.3 Verify capability-probing priority behavior.