Pier adapter 0.3.9

Pier 0.3.9 fixes stable CLI manifest redirects and makes every automatic
selection or fallback observable in cli-resolution.json. Fallback warnings
include a bounded reason, selected version, and archive checksum.

Manifest downloads follow bounded trusted HTTPS redirects, reject compressed
or oversized metadata, and preserve release identity/checksum validation.
Signed download URLs are excluded from HTTP request diagnostics. A running
task keeps the binary selected at setup; new tasks resolve the stable release
again. Explicit archive pins remain explicit.

The accompanying server and CLI release changes retain qualified older worker
identities independently of the current server build and require fresh serving
production admission before promoting a new CLI. npm follows the guarded
canonical publication. Unknown workers remain rejected.

All 385 adapter tests passed against the release wheel built from merged
reason-machines/monorepo commit e7d5780c88b1b6d26f085bd349433778eef2da1b,
PR #11708. Fault regressions cover redirects, size limits, log redaction,
fallback visibility, cancellation, and per-task version selection.

Assets: source archive, Python wheel, and SHA256SUMS. The examples tag identifies
the documentation repository; the adapter source is the monorepo commit above.
End-to-end run evidence will be added after verification. Runtime completion
and benchmark task correctness are separate results.