Pin golangci-lint to avoid nilness panic on main

[samuv]

Summary

CI on main is failing: golangci-lint panics during the staticcheck /
nilness fact analysis with internal error: unhandled builtin recover
while analyzing github.com/getsentry/sentry-go (a dependency of
pkg/sentry). See the failing run:
https://github.com/stacklok/toolhive/actions/runs/32346960123/job/96357620328

Root cause: .github/workflows/lint.yml used to pin
golangci-lint-action's version input (v2.0.1), but that pin was
silently dropped when the action was bumped to v8.0.0. Since then, CI
floats to golangci-lint's latest release. v2.13.0 (released
2026-08-19) bundles a release-candidate build of staticcheck
(honnef.co/go/tools@v0.8.0-rc.1), which crashes on this codebase.
This is an upstream bug — pkg/sentry/sentry.go itself never calls
recover().

• Pin golangci-lint-action's version input back to v2.12.2, the
  last stable release before the regression, until upstream ships a
  fix.

Fixes #

Type of change

• Bug fix

Test plan

• Unit tests (task test)
• E2E tests (task test-e2e)
• Linting (task lint-fix)
• Manual testing (describe below)

Confirmed via gh release list that v2.12.2 (2026-05-06) predates
the v2.13.0 (2026-08-19) release that introduced the staticcheck RC
dependency, and that this repo has no replace directive affecting
github.com/getsentry/sentry-go. This is a CI-only config change;
correctness will be confirmed by this PR's own lint job running
against the pinned version.

Special notes for reviewers

Once golangci-lint ships a release with a fixed honnef.co/go/tools
version, the version: v2.12.2 pin (and its explanatory comment)
should be removed so CI floats to latest again.

Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 77.73%. Comparing base (b6aa047) to head (3a9126a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6393      +/-   ##
==========================================
+ Coverage   77.66%   77.73%   +0.06%     
==========================================
  Files         748      748              
  Lines       71826    71826              
==========================================
+ Hits        55787    55836      +49     
+ Misses      16034    15985      -49     
  Partials        5        5              

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