Summary

Reverts the two version-bump commits that landed today so the
workspace is back at 2026.5.17-beta.12. Tags
v2026.5.25-beta.13, v2026.5.25-beta.14 and the matching
sdk/go/v0.20260525.0-beta.13 / sdk/go/v0.20260525.0-beta.14
have been deleted from the remote and locally; corresponding GitHub
Releases were already removed by the maintainer.

All other work on main since v2026.5.17-beta.12 (315+ PRs,
including #5714 nix flake source-filter fix) is preserved — this
PR only touches files that the two bump commits touched.

Commits reverted

• 3bb6726f — chore: bump version to v2026.5.25-beta.14 (#5715)
• d0ac934f — chore: bump version to v2026.5.25-beta.13 (#5711)

Done with git revert --no-edit so the diffs are exact inverses; no
hand-edits.

Resulting workspace version

Cargo.toml                                : 2026.5.17-beta.12
sdk/rust/Cargo.toml                       : 2026.5.17-beta.12
sdk/javascript/package.json               : 2026.5.17-beta.12
sdk/python/setup.py                       : 2026.5.17b12   (PEP 440)
packages/whatsapp-gateway/package.json    : 2026.5.17-beta.12
openapi.json                              : 2026.5.17-beta.12
crates/librefang-desktop/tauri.conf.json  : 26.5.32182     (Tauri numeric encoding)
CHANGELOG.md                              : top section is `## [Unreleased]`

What was NOT touched

• npm @librefang/sdk (2026.5.25-beta.14 already published — handle
  separately if needed; 2026.5.25-beta.13 never published because
  the publish job's NPM_TOKEN had expired at the time)
• crates.io librefang (2026.5.25-beta.13, 2026.5.25-beta.14 are
  immutable — cargo yank them out-of-band if needed)
• PyPI librefang (immutable — yank out-of-band if needed)
• Docker ghcr.io/librefang/librefang:2026.5.25-beta.13 /
  :2026.5.25-beta.14 (mutable, can delete via registry)

Per maintainer direction (其他的不用管), this PR intentionally does
not touch downstream artifacts.

Verification

• git revert is a diff inversion; no behavior changes to runtime
  code. Files touched are version strings and codegen baselines that
  the bump commits had updated.
• CHANGELOG: the ## [2026.5.25] headings the bumps added are
  removed; ## [Unreleased] is now the leading section.
• xtask/baselines/openapi.sha256 and xtask/baselines/agent.sha256
  are reverted alongside the openapi/agent files they shadow, so the
  drift check stays consistent.
• I did not run cargo (per repo policy) — CI is the authoritative
  check.

Follow-up

When the next release is cut (just release), it will bump from
2026.5.17-beta.12 → 2026.5.25-beta.13 again (CalVer + next beta
slot). If reuse of beta.13 / beta.14 numbers is undesirable, pin
--version on the next cargo xtask release invocation. The npm /
crates.io / PyPI already-immutable beta.13 / beta.14 versions
will not collide with a re-issue at the same number because they
remain published; only the tag + GH Release would need to be
distinct or this PR would need an explicit version skip.