Scope usage per CLAUDE_CONFIG_DIR, includin authentication - #266

Upstream: Extra Usage Limit widget (sirmalloc#756), live widget preview while picking (sirmalloc#755), Fast Mode widget (sirmalloc#754), transcript block fallback fixes (sirmalloc#752), editor keys on a global install (sirmalloc#751), git cache TTL (sirmalloc#750), npx cached copy skip (sirmalloc#749), Block Usage hide at 100% (sirmalloc#747), Block Reset Timer hide until 100% (sirmalloc#697), fish-style branch abbreviation (sirmalloc#614), jj detached HEAD (sirmalloc#705), hooks save warning (sirmalloc#703), dev reload (sirmalloc#700), merge ends at a hidden widget (sirmalloc#698), Block Forecast and Block Limit Timer widgets (sirmalloc#699), contributor guide (sirmalloc#706), POSIX path case fix (sirmalloc#707), whitespace-distinct conflict filenames (sirmalloc#709), Quick Start reorder (sirmalloc#715), bunx launch guidance (sirmalloc#714), jj diff summary counts (sirmalloc#711), powerline manual separators (sirmalloc#713), keychain credential by account (sirmalloc#532), Keychain probe timeout (sirmalloc#760), usage cache scoped per CLAUDE_CONFIG_DIR (sirmalloc#266), test isolation (sirmalloc#717, sirmalloc#753), dev-dependency bumps (sirmalloc#745)

Conflicts resolved per the standard-resolution table; fork deletions re-applied.

Hand edits outside conflicts:
- src/utils/global-command-resolution.ts: fork-rename (ccstatusline@ -> ccstatusline-usage@ in upstream's new bunx pattern)
- src/utils/__tests__/global-package-manager.test.ts: fork-rename (package dir ccstatusline-usage in upstream's new tests)
- src/utils/usage-fetch.ts: compat fix - cacheUsageData gained a fetchedAtMs arg (upstream sirmalloc#266); adapted the fork-only fetchFreshUsageData call site
- src/utils/__tests__/usage-fetch.test.ts: compat fixes - cache/lock now hashed per CLAUDE_CONFIG_DIR (usageFilePath helper) in four fork tests; upstream fableUsage renamed to fork's weeklyFableUsage; seedUsageCache takes TokenHome
- src/utils/__tests__/usage-prefetch.test.ts: compat fix - mockFetchUsageData renamed to upstream's mockFetchUsage in cleanly-merged tests
- README.md: took upstream's Quick Start move (sirmalloc#715) and dropped the fork's old copy; fork-rename of its ccstatusline@ specifiers; links to fork-deleted docs (docs/USAGE.md, docs/WINDOWS.md) replaced with the fork's inline text
- CONTRIBUTING.md: links to the fork-deleted docs/DEVELOPMENT.md pointed at the README Development section
- docs/test-retirements.md: ledger entries for the 12 upstream test renames (sirmalloc#697, sirmalloc#698, sirmalloc#700, sirmalloc#705, sirmalloc#713, sirmalloc#760)

The usage lock held every fetch off, whichever login made it. A 429 for one
access token kept the usage widgets on cached numbers or "Rate limited" until
its Retry-After ran out, often an hour, even after Claude Code refreshed the
login: the new token got a 200 as soon as the lock file was deleted by hand.

A lock written for the API refusing a request, with a 429 or a lasting
answer such as a 401, now names the fingerprint of the access token the
request was sent with, and a fetch with another token skips it. That covers
both read paths: the known login's, which a token refresh leaves by changing
the login's stamp, and the one that reads the credentials. The fingerprint is
the access token's, since a refresh may keep the refresh token the cache's
fingerprint comes from. A lock without one (the in-flight record, a failure
of the server, the network or the response, a file from an older version)
still holds every login off.

Profiles used side by side share the lock file, so a request that replaces
another token's active lock with its in-flight record puts that lock back
once it succeeds, instead of ending the other login's backoff early.

Upstream sirmalloc#266 now gives each profile its own lock file, so the part about
profiles sharing one is moot; a token refresh within one profile still
needs the per-token lock.