docs(upstream): record the v0.53.3 release

[sunerpy]

Summary

Records the v0.53.3 release in docs/upstream-sync/UPSTREAM.md:

• the release PR chore: release 0.53.3 #315 merge (81bd7c7), its tag SHA, release workflow run 37143381806 and the published linux-musl digest;
• the black-box acceptance of the downloaded archives against v0.53.2 (checksums, attestations, the padded kind column in search/callers/callees/impact, byte-identical --json and export, an index built by v0.53.2 reported current);
• dated Sync log entries for the padded kind column (fix(cli): pad the kind column in search, callers, callees and impact #314) and for the stand-in executable warm-up (test: run freshly written stand-in executables once before relying on them #317, merged as aef4efb).

Docs only; no code, golden or schema change.

Testing

• make pre-ci passed in the pre-push hook on 69073e2 (fmt-check, docs-check, clippy, tests, UI check, release build and archive smoke).
• python3 scripts/docs-check.py passes.

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Remove the AI attribution trailer

The reviewed commit message ends with 🤖 Generated with [Claude Code](...), which is an AI attribution trailer explicitly prohibited by this repository’s commit discipline. Remove that footer before landing the commit so the permanent history complies with the contributor contract.

AGENTS.md reference: AGENTS.md:L197-L199

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@           Coverage Diff           @@
##             main     #318   +/-   ##
=======================================
  Coverage   95.07%   95.07%           
=======================================
  Files         198      198           
  Lines      109033   109033           
=======================================
  Hits       103659   103659           
  Misses       5374     5374           

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