chore: remove pr-description.md from repo

pr-description.md

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-## fix(feishu): smart message format selection (fixes #1548)
-
-### Problem
-
-Currently, the Feishu channel sends **all** messages as interactive cards (`msg_type: "interactive"`). This is overkill for short, simple replies like "OK" or "收到" — they look heavy and unnatural compared to normal chat messages.
-
-### Solution
-
-Implement smart message format selection that picks the most appropriate Feishu message type based on content analysis:
-
-| Content Type | Format | `msg_type` |
-|---|---|---|
-| Short plain text (≤ 200 chars, no markdown) | Text | `text` |
-| Medium text with links (≤ 2000 chars, no complex formatting) | Rich Text Post | `post` |
-| Long text, code blocks, tables, headings, bold/italic, lists | Interactive Card | `interactive` |
-
-### How it works
-
-1. **`_detect_msg_format(content)`** — Analyzes the message content and returns the optimal format:
-   - Checks for complex markdown (code blocks, tables, headings) → `interactive`
-   - Checks for simple markdown (bold, italic, lists) → `interactive`  
-   - Checks for links → `post` (Feishu post format supports `<a>` tags natively)
-   - Short plain text → `text`
-   - Medium plain text → `post`
-
-2. **`_markdown_to_post(content)`** — Converts markdown links `[text](url)` to Feishu post format with proper `a` tags. Each line becomes a paragraph in the post body.
-
-3. **Modified `send()` method** — Uses `_detect_msg_format()` to choose the right format, then dispatches to the appropriate sending logic.
-
-### Design decisions
-
-- **Post format for links only**: Feishu's post format (`[[{"tag":"text",...}]]`) doesn't support bold/italic rendering, so we only use it for messages containing links (where the `a` tag adds real value). Messages with bold/italic/lists still use cards which render markdown properly.
-- **Conservative thresholds**: 200 chars for text, 2000 chars for post — these keep the UX natural without being too aggressive.
-- **Backward compatible**: The card rendering path is completely unchanged. Only the routing logic is new.
-
-### Testing
-
-Format detection tested against 13 cases covering all content types:
-- ✅ Plain text → `text`
-- ✅ Links → `post`  
-- ✅ Bold/italic/code/tables/headings/lists → `interactive`
-- ✅ Long content → `interactive`
-- ✅ Post format generates valid Feishu post JSON with proper `a` tags
-
-### Changes
-
-- `nanobot/channels/feishu.py`: Added `_detect_msg_format()`, `_markdown_to_post()`, and updated `send()` method