refactor(opentofu): in-progress PR comment updates, unified headers, collapsible output

[xnoto]

Summary

Refactors the pinned PR comment behavior in opentofu.yml (both test and plan jobs):

1. In-progress update before the job runs. A new first step in each job immediately updates the pinned comment to state that a run is in progress and will be updated when it completes, preserving the previous run's output in a collapsible "Previous run output" section (un-nested on repeat cycles so the comment can't accumulate stale history).
2. Unified headers (plan style). Both comments now use:
   • #### OpenTofu Test / OpenTofu test passed. / OpenTofu test failed.
   • #### OpenTofu Plan / OpenTofu plan passed. / OpenTofu plan failed with exit code X.
3. Removed the Validation output (redacted, last 12000 characters) line from the test comment (redaction itself is unchanged).
4. Collapsible output. The output/diff body in both comments is wrapped in a <details> block with summary "View run output". Both comments keep/gain a "View the workflow run" link.

Caller impact

No interface change: inputs, secrets, permissions, runner labels, triggers, emitted checks, and artifacts are unchanged. Callers (tfroot-aws, tfroot-gcp, tfroot-libvirt, tfroot-github, tfroot-cloudflare, and any other @main consumers) pick this up on their next run without modification. Fork-PR behavior is unchanged (no comment steps run; the test in-progress step uses the same same-repository condition as the existing report step). The apply job is untouched.

Notes

• The in-progress steps reuse the already-pinned actions/github-script@3a2844b... # v9.0.0 and existing pull-requests: write job permissions.
• The test ANSI-strip regex is byte-identical to main (/\u001b\[[0-?]*[ -/]*[@-~]/g).

Validation

• Repo CI (_ci.yml: pre-commit/actionlint/gitleaks) on this PR.
• Behavioral verification of the new comment lifecycle will be observable on the next consumer-repo PR run after merge (no workflow dispatch performed here).

[github-actions]

Shared workflows CI passed

View the workflow run.

Validation output (redacted, last 12000 characters)

[INFO] Initializing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Initializing environment for https://github.com/gitleaks/gitleaks.
[INFO] Initializing environment for https://github.com/rhysd/actionlint.
[INFO] Installing environment for https://github.com/pre-commit/pre-commit-hooks.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
[INFO] Installing environment for https://github.com/gitleaks/gitleaks.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
[INFO] Installing environment for https://github.com/rhysd/actionlint.
[INFO] Once installed this environment will be reused.
[INFO] This may take a few minutes...
check for case conflicts.................................................Passed
check for merge conflicts................................................Passed
check for broken symlinks............................(no files to check)Skipped
check vcs permalinks.....................................................Passed
detect destroyed symlinks................................................Passed
detect private key.......................................................Passed
mixed line ending........................................................Passed
trim trailing whitespace.................................................Passed
Detect hardcoded secrets.................................................Passed
Lint GitHub Actions workflow files.......................................Passed