feat: replace tabId with targetId as cross-layer page identity

[jackwener]

Summary

• Use Chrome CDP targetId (UUID) as the canonical page identity across all layers (extension → daemon → CLI), demoting tabId to an extension-internal routing detail
• Add identity.ts module for bidirectional targetId ↔ tabId mapping with lazy refresh via chrome.debugger.getTargets()
• Add sendCommandFull() to daemon-client for returning page identity alongside response data

Changes

Layer	File	What changed
Extension	identity.ts	New module — resolveTargetId(), resolveTabId(), evictTab(), refreshMappings()
Extension	protocol.ts	Command.page and Result.page fields (targetId)
Extension	background.ts	resolveCommandTabId() + pageScopedResult() helpers; all page-scoped handlers emit targetId
CLI	daemon-client.ts	DaemonCommand.page, DaemonResult.page, new sendCommandFull()
CLI	page.ts	_page stores targetId; goto()/selectTab() extract from sendCommandFull()
CLI	record.ts	injectedPages tracks by targetId instead of tabId
CLI	types.ts	IPage.getActivePage() returns targetId
Infra	vitest.config.ts	Extension tests added to test projects
Infra	package.json	npm test includes --project extension

Design constraints

1. workspace ≠ page — workspace is task context, page is the CDP target
2. page only in page-scoped responses — navigate, exec, screenshot, tabs:select, etc.
3. Missing page → hard error — never guess or fall back silently

Test plan

• All 551 tests pass (0 failures, 2 pre-existing skips)
• TypeScript compiles clean (no new errors)
• Extension tests included in npm test and CI
• Manual: opencli run navigates and returns targetId in page field
• Manual: tab switch via selectTab() updates _page correctly