fix(github): emit repo under canonical repo key so automations match

[viktormarinho]

Context

Full webhook path worked end-to-end — verified in production logs:

```
[Webhook] ← delivery=b9903d64… event=issues hook=609463396
[Webhook] → delivery=b9903d64… event=github.issues.opened subject=decocms/studio installation=120173638 connection=conn_LY5860COJlW4bIZqLufd5 sender=viktormarinho action=opened
[Webhook] ✓ delivery=b9903d64… mesh callback delivered (202)
```

Mesh accepted with 202 but the matching automation never fired. Confirmed the Studio-side trigger was configured correctly:

```
automation.active = true
trigger.event_type = 'github.issues.opened'
trigger.connection_id = 'conn_LY5860COJlW4bIZqLufd5'
trigger.params = {"repo": "decocms/studio"}
```

Root cause

`EventTriggerEngine.paramsMatch` in Studio does strict key equality:

```ts
return Object.entries(params).every(([key, value]) => data[key] === value);
```

So it looked up `data.repo` — but our webhook handler was shipping the repo under `data.repository`, leaving `data.repo === undefined` and the match failed silently.

Fix

Emit the repo full name under the canonical `repo` key (what the trigger params schema in `trigger-store.ts` declares). Kept `repository` as an alias for downstream consumers that might already depend on it.

Test plan

• After deploy, create an issue in `decocms/studio`. Expect `[Webhook] ✓ delivery=… mesh callback delivered (202)` in worker logs as before, AND a new `threads` row in Studio's DB with `status = in_progress → completed`.

🤖 Generated with Claude Code

---

Summary by cubic

Fixes GitHub webhook events so the repo is emitted under the canonical repo key, allowing automations that filter by repo to match. Keeps repository as an alias for backward compatibility.

^{Written for commit 717388f. Summary will update on new commits.}