feat: optional findings telemetry — emit runs+findings to a gadfly-reports store

After each review the binary POSTs the run + its heuristically-extracted findings to GADFLY_FINDINGS_URL (off unless set). Advisory: any error only goes to stderr — never touches stdout, the exit code, or the review. stdlib net/http only (no new deps). entrypoint.sh derives GADFLY_REPO/GADFLY_PR and passes through GADFLY_FINDINGS_URL/GADFLY_FINDINGS_TOKEN. Also renames store references from the old 'docket' name to 'gadfly-reports'.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

README.md

@@ -254,6 +254,26 @@ The reviewer binary reads these (the stub/entrypoint set sane defaults):
 | `GADFLY_MAX_DIFF_CHARS` | 60000 | diff chars embedded in the prompt (full diff via `get_diff`) |
 | `GADFLY_TRIGGER_PHRASE` | `@gadfly review` | comment phrase that re-triggers |
 | `GADFLY_ALLOWED_USERS` | *(collaborators)* | comma-separated allow-list for comment triggers |
+| `GADFLY_FINDINGS_URL` | — | gadfly-reports store base URL; set to enable findings telemetry (off when empty) |
+| `GADFLY_FINDINGS_TOKEN` | — | bearer token for the gadfly-reports store (sent as `Authorization: Bearer …`) |
+| `GADFLY_REPO` | *(from `GITEA_API`)* | `owner/repo` slug stamped on emitted runs/findings (set by `entrypoint.sh`) |
+| `GADFLY_PR` | *(from event)* | PR number stamped on emitted runs/findings (set by `entrypoint.sh`) |
+
+## Findings telemetry (optional)
+
+Gadfly can record what it found so model quality can be tracked over time. It is
+**off by default** and purely advisory: set **`GADFLY_FINDINGS_URL`** to a
+[gadfly-reports](https://gitea.stevedudenhoeffer.com/steve/gadfly-reports) store base URL and,
+after each review, the binary best-effort `POST`s the run (`/runs`) and the
+findings it surfaced (`/reports`) to that store. Add **`GADFLY_FINDINGS_TOKEN`**
+to send an `Authorization: Bearer …` header. `entrypoint.sh` supplies the run
+context (`GADFLY_REPO`, `GADFLY_PR`) automatically.
+
+Findings are extracted heuristically from each lens's markdown — a `path:line`
+reference anchors a finding, titled by the nearest preceding heading / numbered
+item / bold lead-in. The emit is strictly best-effort: a short (~10s) timeout,
+any error (or a non-2xx response) is logged to stderr only, and it **never**
+changes the review output or the exit code.
 
 ## Building locally