Prepare tooling 0.8.0 release

[hdamker]

What type of PR is this?

documentation

What this PR does / why we need it:

Prepares the numbered tooling 0.8.0 release. It consolidates the changes that landed on main since v0.7.1:

• x-correlator documentation checks — new rules S-039 (request header undocumented) and S-040 (response header undocumented) (feat(validation): check x-correlator documentation #376)
• Unused-component detection made discriminator-aware — S-211 rewrite, gated to OpenAPI only (Make unused-component detection discriminator-aware #378)
• P-006/P-007/P-008 severity ramp migrated to target_api_status — no behavior change (fix(validation): migrate P-006/P-007/P-008 severity ramp to target_api_status #381)
• P-016 rewritten as a per-field sinkCredential writeOnly check (fix(validation): rewrite P-016 as a per-field sinkCredential writeOnly check #383)
• S-036 parameter casing: allow Design-Guide-defined filtering-operation suffixes (.gte, .gt, .lte, .lt) (fix(validation): allow Design Guide filter suffixes in parameter casing #389)
• Dependency bumps: @redocly/cli 2.37.0→2.39.0 (chore(deps): bump @redocly/cli from 2.37.0 to 2.39.0 in /validation #374), actions/setup-python 6→7 (chore(deps): bump actions/setup-python from 6 to 7 #384), actions/setup-node 6→7 (chore(deps): bump actions/setup-node from 6 to 7 #385), @stoplight/spectral-cli →6.16.2 (chore(deps): bump @stoplight/spectral-cli from 6.16.1 to 6.16.2 in /validation #386), fast-uri/brace-expansion security patches (fix(deps): bump fast-uri, brace-expansion to patched versions in validation/ #391)

Changes: VERSION.yaml → 0.8.0, a v0.8.0 CHANGELOG.md section, and a README release-information tag touch-up. Two new rule IDs (S-039/S-040) plus behavior rewrites of S-211, P-016, and S-036 make this a minor release, not a patch.

Which issue(s) this PR fixes:

Fixes #

Special notes for reviewers:

Numbered release PR — v1-rc is moved to the released commit after merge. Both regression canaries are green at HEAD (247ed6e): Validation Regression 11/11 PASS, RA Regression green at the last RA-scope-touching commit (c506a7b). The actions/setup-python/actions/setup-node major-version bumps (#384/#385) touch release-automation-reusable.yml; the canary-only gate for those two PRs was already reviewed and accepted as sufficient (mechanical version-pin-only bumps, every call site covered, no input changed) — no fresh manual E2E needed for this release.

Changelog input

 release-note
Prepare tooling 0.8.0 release.

Additional documentation

This section can be blank.

docs
NONE

[rartych]

LGTM
Some fixes are awaited by Subprojects preparing API release candidates.