test: share the handler/cache fixtures from ctx::test_support

The same fixtures were rebuilt in five test modules: a `CachedPost`
literal in `link_cache.rs`, `handlers/urls.rs` and twice in
`send/mod.rs`, the edit-before-forward prompt in `handlers/mod.rs` and
`handlers/callback.rs`, and a scripted API error in both handler
modules. They now live in `ctx::test_support` next to `TestStores`:

- `cached_photo()` — the canonical cached post (photo + file id at
  `https://x.com/u/status/1`, key `twitter:1`); tests mutate the fields
  they care about, as the caption-quote test already did.
- `seed_prompt(template, created_at)` + `PROMPT_ID`/`FORWARDED_ID` —
  the prompt record, the chat template and the bound forward channel.
  The two former copies differed only in which knob the caller set (the
  callback tests backdate it for the expiry cases, the reply tests pick
  the template), so the union is one helper.
- `api_error(message)` — construction only; each test module keeps its
  own message constant, because the wording is what that module's path
  answers with (`chat not found` vs `message not found`).

`send/mod.rs`'s `cached_sequence_cache_data()` (which re-extracted the
post out of the task it had just built) is gone: the two settle tests
seed the cache from the same builder the task uses.

No behaviour change: the values are the ones the tests used except
`file_id` (`AgAC-file-id` everywhere, asserted in the link-cache
round-trip) and `sensitive` (the unasserted `true` in the link-cache
fixture), and every test still passes unchanged.

Verified: `cargo fmt`, `cargo clippy --workspace --all-targets --locked
-- -D warnings` and `cargo test --workspace --locked` (180 passed, 14
ignored).

AGENTS.md

@@ -45,7 +45,7 @@ The `x-media` library: `site::fetch(url)` dispatches through the `SITES` registr
 | `crates/xmedia-bot/src/state.rs` | `ChatStore`: parking_lot `Mutex<HashMap>` cache + SQLite write-through (`chat_state` table) |
 | `crates/xmedia-bot/src/link_cache.rs` | `LinkCache`: SQLite-backed cache (`link_cache` table) of successfully sent posts — raw caption fields + Telegram `file_id`s; repeat links re-send locally (no fetch/upload), TTL + prune, invalidated on permanent send failure |
 | `crates/xmedia-bot/src/queue.rs` | `PersistentTaskQueue`: SQLite-backed queue (`tasks` table), `QUEUE_WORKERS = 4` concurrent workers (lease via `BEGIN IMMEDIATE` + `locked_until` TTL), retry→dead-letter, a `lease_token` fence: `lease_next` stamps a random token and every write-back (heartbeat, `delete`, `reschedule`, `mark_done`) is guarded by it, so a lease that expired and was re-leased cannot be written by its former holder — a lost lease stops the attempt instead; a finished row's `DELETE`/reschedule retried and a failed delete falling back to a `done` tombstone (the lease query and the sweep only look at `pending`/`in_progress`, so a task that already ran cannot be resurrected and re-run), `notify_one` worker wakeup plus a separate `Notify` for the 30 s lease-expiry sweep (a shared one let the sweep steal the workers' wakeup permit; the sweep does notify the workers after it actually recovered a row, since a recovered task is due immediately while every worker may be parked on `notify` with no pending row to sleep on), `busy_timeout` on all connections |
-| `crates/xmedia-bot/src/ctx.rs` | `AppContext`: the injected collaborators (`sender` + `ChatStore`/`PersistentTaskQueue`/`LinkCache`/`Config`), `from_statics` for production and the `CONTEXT` static the worker closures hold. `test_support::TestStores` backs handler tests with a tempdir store set |
+| `crates/xmedia-bot/src/ctx.rs` | `AppContext`: the injected collaborators (`sender` + `ChatStore`/`PersistentTaskQueue`/`LinkCache`/`Config`), `from_statics` for production and the `CONTEXT` static the worker closures hold. `test_support::TestStores` backs handler tests with a tempdir store set, and the module also carries the fixtures those tests share — the canonical cached post (`cached_photo`), the edit-before-forward prompt (`seed_prompt` with its `PROMPT_ID`/`FORWARDED_ID`) and a scripted API error (`api_error`) — so no two test modules keep their own copies |
 | `crates/xmedia-bot/src/send/` | `send/mod.rs`: `Task`/`MediaItemPayload` payloads, `SendError`/`Classification`, `send_media_sequence`/`send_animation`/`forward_messages`; `send/input_media.rs`: payload → `InputFile`/`InputMedia` + `build_media_group` (caption on the first item only); `send/upload.rs`: the download-and-reupload fallback (`prepare_upload_item`/`send_batch_via_upload`, photo downscale handoff); `send/post_send.rs`: link-cache write, `KEEP_ALIVE` registry, `settle_task`, `post_send_actions`, `handle_task`/`dead_letter_notify` |
 | `crates/xmedia-bot/src/media_sender.rs` | `MediaSender` trait: the user-flow surface (`send_media_group`/`send_animation`/`copy_messages`/`send_message`/`answer_callback_query`/`edit_message_caption`/`delete_message`/`send_chat_action`) implemented by teloxide `Bot` (per-chat rate-limited) and by a recording `MockSender` in tests. Admin/setup APIs (`get_chat`, `set_my_commands`, …) stay on the concrete `Bot` |
 | `crates/xmedia-bot/src/rate_limit.rs` | Per-chat token bucket (`CAPACITY = 20`, ~20 msg/min refill) paced before sends reach the API so batch forwards don't trip flood control |