fix(renovate): the config was INVALID, so the first manual run errored out

The operator ran the Renovate workflow manually and it failed. The cause is not
the workflow: renovate.json was never a valid Renovate config. It carried five
pseudo-comment keys (_comment, _kubernetes_comment, _unmanageable_comment,
_ignorePaths_comment, _docker_comment) because JSON has no comments, and
Renovate REJECTS unknown top-level options. Proven with the official validator:

  ERROR: Found errors in configuration
    Invalid configuration option: _comment
    Invalid configuration option: _docker_comment
    Invalid configuration option: _ignorePaths_comment
    Invalid configuration option: _kubernetes_comment
    Invalid configuration option: _unmanageable_comment

This is the SECOND independent reason Renovate never worked, on top of PR #77's
cron firing outside renovate.json's own schedule window. Either alone was enough
to produce "nothing ever happens"; #73 shipped both.

Converted renovate.json -> renovate.json5. JSON5 permits real // comments and
Renovate discovers renovate.json5 natively; nothing in .gitea/ or ci/ pins the
old filename and no RENOVATE_CONFIG_FILE is set. Every word of the original
rationale is preserved as positioned comments (74 comment lines) rather than
flattened into a description string.

Verified the conversion dropped nothing: 18 non-comment keys before and after,
no missing/extra keys, no changed values, docker: {enabled: true} still present.
The validator now returns "Config validated successfully".

DISPROVED while here: `enabledManagers` containing bare `regex` was suspected of
needing to be `custom.regex` (which would silently disable every inline
`# renovate:` marker). The validator accepts `regex`; unfounded, unchanged.

Renovate has still never completed a run -- this fixes one of two blockers and
nothing in the gate catches an invalid config. See the handoff.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

decisions/2026-10-18-renovate-invalid-config.md

@@ -0,0 +1,78 @@
+---
+date: 2026-10-18
+branch: fix/renovate-invalid-config
+title: "renovate.json was invalid, so the first manual run errored out"
+---
+
+## What changed
+
+The operator ran the Renovate workflow manually and it **failed**. The cause is not the workflow:
+**`renovate.json` was never a valid Renovate config.**
+
+It carried five pseudo-comment keys — `_comment`, `_kubernetes_comment`, `_unmanageable_comment`,
+`_ignorePaths_comment`, `_docker_comment` — because JSON has no comments. Renovate **rejects unknown
+top-level options**, so the entire config failed validation. Proven with the official validator
+rather than inferred:
+
+```
+$ podman run --rm -v "$PWD/renovate.json:/tmp/renovate.json:ro,Z" \
+    ghcr.io/renovatebot/renovate renovate-config-validator /tmp/renovate.json
+ERROR: Found errors in configuration
+  Invalid configuration option: _comment
+  Invalid configuration option: _docker_comment
+  Invalid configuration option: _ignorePaths_comment
+  Invalid configuration option: _kubernetes_comment
+  Invalid configuration option: _unmanageable_comment
+```
+
+This is the second independent reason Renovate had never worked, on top of PR #77's cron firing
+outside `renovate.json`'s own schedule window. Either alone was sufficient to produce "nothing ever
+happens"; #73 shipped both.
+
+**Converted `renovate.json` → `renovate.json5`.** JSON5 permits real `//` comments, and Renovate
+discovers `renovate.json5` natively — nothing in `.gitea/` or `ci/` pins the old filename (only
+prose inside comments), and no `RENOVATE_CONFIG_FILE` is set. Every word of the original rationale
+is preserved as comments positioned next to what it explains, which a flattened `description`
+string would have lost.
+
+A header on the new file records the failure, the validator command, and the instruction to run it
+before committing — this class of bug is invisible to the repo's own gate.
+
+## What I verified
+
+* **The exact failure**, from the official validator, quoted above. Not read off a log, not inferred
+  from the workflow.
+* **The fix validates**: the same validator against `renovate.json5` returns
+  `INFO: Config validated successfully against 1 file(s)`.
+* **Nothing was dropped in the conversion**, checked programmatically against `git show
+  HEAD:renovate.json`: 18 non-comment keys before, 18 after, **no missing keys, no extra keys, and
+  no key whose value changed**. `docker: {enabled: true}` confirmed still present — the validator
+  prints a normalisation diff that mentions it, which is its own migration suggestion, not a
+  removal.
+* **74 comment lines survive** in the new file, so the rationale is intact.
+* **`RENOVATE_TOKEN` exists** as a repository Actions secret (listed by name via the Gitea API), so
+  the workflow's fail-hard preflight is satisfied.
+* **A suspicion was DISPROVED:** `enabledManagers` containing bare `regex` was thought to need to be
+  `custom.regex`, which would have silently disabled every inline `# renovate:` marker. The
+  validator accepts `regex`, so that concern was unfounded and nothing here changes it.
+* Nothing functionally references `renovate.json` by name — `grep -rn "renovate\.json" .gitea/ ci/
+  conformance/` returns only comment prose.
+
+## What I did NOT verify
+
+* **Renovate has still never completed a run.** This removes one of two blockers; PR #77 removes the
+  other. Neither is merged, so **no successful Renovate run has been observed** and I cannot say the
+  bot works — only that these two specific defects are fixed.
+* **I did not re-run the workflow after the fix.** The honest test is a `workflow_dispatch` with
+  `dry_run: true` once both this and #77 are merged. Expect ~30 dependencies behind, rate-limited to
+  `prHourlyLimit: 2` / `prConcurrentLimit: 5`.
+* **Whether the managers actually extract anything.** A valid config that matches no files is still
+  a no-op. The dry-run log's per-manager dependency counts are the only thing that proves the
+  `managerFilePatterns` are right, and I have not seen them.
+* **Whether `renovate.json5` is honoured by the pinned Renovate version in the workflow.** JSON5
+  discovery is long-standing and the validator accepted the file, but the workflow's image tag was
+  not cross-checked against the version that added it.
+* **Nothing in the gate catches an invalid Renovate config.** This bug would have recurred silently.
+  A one-line L0 check shelling out to `renovate-config-validator` would close it; it is not written
+  here, and `conformance/**` is a sensitive path.
+* I did not re-measure branch protection or runner state (CLAUDE.md §2b).