v0.5.0

v0.5.0 — per-route login gate for settings-mode sync

Settings-mode sync now refuses to write or revive routes that have no
configured credential: when /logout clears a stored key and the next
auto-refresh fires, the round would otherwise happily re-write
settings.models for the freshly-unconfigured provider. Two layers are
consulted in order — credentials seam describe(ref).configured first,
then the launch-environment snapshot get(ref).value as fallback — and
only a miss on both layers skips the route with one report line.

Two new optional peers (@deepseek-ai/dsh-credentials,
@deepseek-ai/dsh-launch-environment) ship as optional peerDependencies,
dev-pinned to the 0.1.5-rc.2 closure; hosts that expose neither still
get a clean miss.

Test surface grows to 10 suites with 188 assertions (route-credential
suite added; real-cordis and writer-overrides legs extended to cover
the gate end-to-end).