feat(send): quote a long post's text in an expandable blockquote

A post whose text (the split `title` plus `content`, joined by
`site::compose_text`) reaches `CAPTION_QUOTE_TEXT_CHARS` — default 200,
`0` disables — now has that text wrapped in `<blockquote expandable>`
inside its caption, leaving the URL and author line outside the quote.

Applied at the send boundary (`send_media_sequence`, `send_animation` and
the inline answers), where the caption is already truncated and the same
cache snapshot supplies the text, so a fresh send, a link-cache resend
and a queued retry all decide identically. The text is located as what
follows the author link, with the visible prefix accepted as a match
because `truncate_caption` may cut inside it — that keeps the longest
posts, the ones that most need folding, quoted. Captions whose layout
moves the text elsewhere (pixiv's title-inside-a-link, a `/set_format`
that puts `{title}`/`{content}` first) stay unquoted rather than risking
a blockquote nested in a tag, and a caption that already carries one is
never wrapped again.

Telegram measures a caption *after entities parsing*, so the tags cost no
length and the 1024-character limit cannot be breached; retries replay
the unwrapped caption, so a threshold change takes effect immediately.
The edit-before-forward rewrite stays unquoted by design.

Verified against Telegram: a media-group caption built this way comes
back with `caption_entities` `url` @0, `text_link` @50,
`expandable_blockquote` @56 — the quote starts after the author line.

AGENTS.md

@@ -92,7 +92,7 @@ Docker: `docker build -t tgxmb .` then `docker run --rm -d --name tgxmb --env-fi
 - Package manager: **Cargo** (workspace with path dep `x-media` ← `xmedia-bot`). No `[workspace.package]`/shared deps — each crate lists deps independently.
 - **TLS is rustls end-to-end** (no native-tls/openssl in the tree, no libssl in the Docker runtime image): `teloxide` is declared `default-features = false` with `["webhooks-axum", "macros", "rustls", "ctrlc_handler"]` (the removed `default` also carried `native-tls` and `ctrlc_handler` — the latter must stay); x-media's reqwest is `default-features = false` with `["json", "rustls-tls"]` (webpki-roots baked in, so the image ships no CA bundle). One reqwest 0.12.28 in the lock.
 - **Versioning**: bump the version in all three places (`crates/x-media/Cargo.toml`, `crates/xmedia-bot/Cargo.toml`, `Cargo.lock`) and **keep `README.md`, `README.en.md` and `AGENTS.md` in sync with the code on every bump**, then commit (`chore: bump version to X.Y.Z`), create an annotated tag `vX.Y.Z`, and push branch + tag (the tag push triggers the Docker Hub build). The tag must equal both crate versions: `.github/workflows/docker.yml` verifies that before building, and `--locked` verifies the lock file.
-- Config is **environment-variable driven** (dotenv loads `.env`, gitignored; no `.env.example` exists). Key vars: `TELOXIDE_TOKEN` (required), `PIXIV_REFRESH_TOKEN`, `TWITTER_AUTH_TOKEN` (optional; x.com `auth_token` cookie — enables the logged-in GraphQL fallback that fetches NSFW tweets syndication withholds), `BILIBILI_COOKIE` (optional; whole bilibili cookie string — bilibili dynamics fetch anonymously and add their own device cookies, this only rescues an egress IP that bilibili has hard-flagged with `-352`/412), `BOT_ADMIN` (comma-separated ids), `EDIT_MESSAGE_TTL_SECONDS` (default 86400), `LINK_CACHE_TTL_SECONDS` (default 604800), `DATA_DIR` (default `data`, CWD-relative; the SQLite dir, auto-created), `WEBHOOK`/`WEBHOOK_URL`/`WEBHOOK_LISTEN`/`WEBHOOK_PORT`/`WEBHOOK_CERT`/`WEBHOOK_SECRET_TOKEN` (webhook mode requires URL/listen/port, `.expect`ed; `WEBHOOK_CERT` is Telegram-facing self-signed validation only — TLS must be terminated by a reverse proxy), `RUST_LOG`, `TELOXIDE_PROXY`, `LOCAL_USER_ID` (entrypoint only).
+- Config is **environment-variable driven** (dotenv loads `.env`, gitignored; no `.env.example` exists). Key vars: `TELOXIDE_TOKEN` (required), `PIXIV_REFRESH_TOKEN`, `TWITTER_AUTH_TOKEN` (optional; x.com `auth_token` cookie — enables the logged-in GraphQL fallback that fetches NSFW tweets syndication withholds), `BILIBILI_COOKIE` (optional; whole bilibili cookie string — bilibili dynamics fetch anonymously and add their own device cookies, this only rescues an egress IP that bilibili has hard-flagged with `-352`/412), `BOT_ADMIN` (comma-separated ids), `EDIT_MESSAGE_TTL_SECONDS` (default 86400), `LINK_CACHE_TTL_SECONDS` (default 604800), `CAPTION_QUOTE_TEXT_CHARS` (default 200; a post whose text — the `title` plus `content` joined, see `site::compose_text` — reaches this length gets that text wrapped in an expandable blockquote inside its caption, the URL and author line staying outside; `0` disables it. Applied at the send boundary in `send::quote_long_caption`, which locates the text as what follows the author link, so a `/set_format` that moves `{title}`/`{content}` elsewhere and pixiv's title-inside-a-link layout opt out; `copy_messages` forwards and queued retries inherit the wrap, while the edit-before-forward rewrite stays unquoted by design), `DATA_DIR` (default `data`, CWD-relative; the SQLite dir, auto-created), `WEBHOOK`/`WEBHOOK_URL`/`WEBHOOK_LISTEN`/`WEBHOOK_PORT`/`WEBHOOK_CERT`/`WEBHOOK_SECRET_TOKEN` (webhook mode requires URL/listen/port, `.expect`ed; `WEBHOOK_CERT` is Telegram-facing self-signed validation only — TLS must be terminated by a reverse proxy), `RUST_LOG`, `TELOXIDE_PROXY`, `LOCAL_USER_ID` (entrypoint only).
 - SQLite via `rusqlite` with `bundled` feature (no system libsqlite needed). DB file `$DATA_DIR/task_queue.db` (default `data/task_queue.db`, CWD-relative — run from the workspace root, or `/app` in Docker; set `DATA_DIR` to pin state anywhere). Mount `./data` and `./cert` volumes.
 - `.gitattributes` enforces LF for `*.sh` (CRLF breaks shebangs in containers). `.gitignore`: `.env`, `data/`, `cert/`, `docker-compose.yml`, `/target`, `.idea/`.
 - Docs are in Chinese (README, AGENTS.md); user-facing bot strings are in English. Keep that split when editing user-facing strings and docs.