Restore ACP usage telemetry / 恢复 ACP 用量遥测

[SivanCola]

Problem

Usage cards and the status-bar cache rate remained empty with current Reasonix ACP releases. The extension only consumed the legacy session/update: usage shape and ignored the namespaced status notifications advertised by Reasonix 1.19+.

Reasonix 1.17.21 did not publish usage over ACP at all, so relaxing the legacy validator could not fix the reported version combination.

Fix

• Discover _reasonix.io/session/status and _reasonix.io/session/status_update through agentCapabilities._meta.
• Validate schema v1 snapshots and matching update envelopes before using them.
• Request an initial status snapshot for new and resumed sessions.
• Map turn and cumulative usage into the existing usage card and status-bar model.
• Reject duplicate or stale sequences so older async updates cannot regress the UI.
• Preserve the legacy session/update: usage path for older compatible backends.
• Extend unit, Extension Host, real-ACP smoke, and VSIX coverage.
• Refresh four transitive development dependencies required by the high-severity audit gate.

Compatibility

Input	Behavior	Result
Reasonix 1.19+ schema v1 capability	Initial snapshot plus live updates are consumed	Usage and cache telemetry display automatically
Legacy backend with session/update: usage	Existing parser and UI path remain unchanged	Backward compatible
Backend without either telemetry surface	No extra request is sent	Existing no-telemetry behavior is preserved
Unknown status schema	Capability and payload are ignored	Fails closed without corrupting UI state
Duplicate or stale sequence	Update is discarded	Newer usage remains visible
Persisted extension data	No schema or storage changes	No migration required

Verification

• npm audit --audit-level=high
• npm run lint
• npm test (51 tests)
• npm run test:vscode
• npm run smoke:acp against Reasonix 1.19.1 with status schema v1
• npm run package:vsix
• npm run verify:vsix-contents

Closes #4