feat(atlas): surface the user's own Gitea repos on stage 05 (#10)

Adds the repos panel from #4's "Not yet shipped" list, following the shipped
issues slice (b2761a4) structurally rather than inventing a second approach:

- internal/atlas/repos.go — RepoNodes(), a pure parser over an already-decoded
  /user/repos response. Archived repos are dropped: the atlas shows where work
  happens, and an archived repo is by definition somewhere it does not.
- internal/gitea/client.go — MyRepos(), same PAT and same contract as MyIssues:
  errors when GITEA_TOKEN is unset so the caller skips the overlay rather than
  issuing an unauthenticated request. That unset path is the one running in
  prod today (#4), so it is tested, not assumed.
- internal/web/handler.go — wired into liveOverlay().

Stage 05 is the right home — repos are what the execution stage acts on — but
#11 had just claimed its `generate` key for stuck-badges, and a stage could
only name one source. So `generate` now accepts either spelling:

    "generate": "ci-jobs"
    "generate": ["stuck-badges", "gitea-repos"]

The bare string stays valid and marshals back as a bare string, so no authored
stage is rewritten and the frontend contract is unchanged. Stages 04 and 08
already share stuck-badges between them; this is the same growth one level in.

The overlay merge also moves out of the handler into atlas.PrependGenerated,
which is unit-testable where the inline loop was not — it sat behind a network
call. It covers the issues path too, and fixes a latent aliasing bug there: the
old `append(liveNodes, authored...)` wrote into the live slice's backing array,
so two stages sharing a key would corrupt each other. That shape is no longer
hypothetical now that stuck-badges spans three stages.

Verified end-to-end both ways: without GITEA_TOKEN the atlas returns 200 with
stage 05's authored nodes intact; with a real token stage 05 serves both
overlays at once — stuck badges, then eight live repos, then the authored
nodes — and a repo with no language emits one tag rather than an empty pill.

task check green (golangci-lint 0 issues, vet, -race).

Closes #10.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

internal/gitea/client.go

@@ -40,6 +40,20 @@ func MyIssues() ([]byte, error) {
 	return get(url, token)
 }
 
+// MyRepos returns the raw /user/repos JSON for the token owner's own
+// repositories. Same PAT and same contract as MyIssues: returns an error if
+// GITEA_TOKEN is unset so callers can skip the overlay gracefully rather than
+// issue an unauthenticated request. Gitea's own visibility rules scope the
+// result, so no additional filtering is applied here.
+func MyRepos() ([]byte, error) {
+	token := os.Getenv("GITEA_TOKEN")
+	if token == "" {
+		return nil, fmt.Errorf("GITEA_TOKEN not set")
+	}
+	url := base() + "/api/v1/user/repos?limit=8"
+	return get(url, token)
+}
+
 // get performs a short-lived GET, optionally with a bearer token, and returns
 // the response body.
 func get(url, token string) ([]byte, error) {