feat: add get_shape_library tool for AI icon discovery (#335)

* feat: add get_shape_library tool for AI icon discovery

- Add server-side tool that returns shape library documentation
- AI can fetch icon/shape names on-demand before generating diagrams
- Includes path traversal protection and input sanitization
- Library index embedded in tool description for discoverability
- Supports 33 libraries: AWS, Azure, GCP, Kubernetes, Cisco, etc.

* fix: improve get_shape_library error handling and imports

- Move fs/path imports to top of file (avoid dynamic imports per call)
- Distinguish file-not-found vs other errors in catch block
- Include invalid input in validation error message
- Log unexpected errors for debugging

* docs: add get_shape_library to system prompt tool list

- Add Tool4 (get_shape_library) to available tools section
- Add usage guidance in 'Choose the right tool' section
- Update AWS icons note to reference get_shape_library for icon discovery

* fix: display get_shape_library tool output in chat UI

* fix: correct state check for get_shape_library output display

* fix: make get_shape_library output respect fold state

* style: auto-format with Biome

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Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>

docs/shape-libraries/webicons.md

@@ -0,0 +1,194 @@
+# webicons
+
+**Type:** mxgraph shapes
+**Prefix:** `mxgraph.webicons`
+
+## Usage
+
+```xml
+<mxCell value="label" style="shape=mxgraph.webicons.{shape};fillColor=#3b5998;strokeColor=none;" vertex="1" parent="1">
+  <mxGeometry x="0" y="0" width="60" height="60" as="geometry" />
+</mxCell>
+```
+
+
+
+## Shapes (177)
+
+- `adfty`
+- `adobe_pdf`
+- `aim`
+- `allvoices`
+- `amazon`
+- `amazon_2`
+- `android`
+- `apache`
+- `apple`
+- `apple_classic`
+- `arduino`
+- `ask`
+- `atlassian`
+- `audioboo`
+- `aws`
+- `aws_s3`
+- `baidu`
+- `bebo`
+- `behance`
+- `bing`
+- `bitbucket`
+- `blinklist`
+- `blogger`
+- `blogmarks`
+- `bookmarks.fr`
+- `box`
+- `buddymarks`
+- `buffer`
+- `buzzfeed`
+- `chrome`
+- `citeulike`
+- `confluence`
+- `connotea`
+- `dealsplus`
+- `delicious`
+- `designfloat`
+- `deviantart`
+- `digg`
+- `diigo`
+- `dopplr`
+- `drawio1`
+- `drawio2`
+- `dribbble`
+- `dropbox`
+- `dropbox2`
+- `drupal`
+- `dzone`
+- `ebay`
+- `edmodo`
+- `evernote`
+- `facebook`
+- `fancy`
+- `fark`
+- `fashiolista`
+- `feed`
+- `feedburner`
+- `flickr`
+- `folkd`
+- `forrst`
+- `fotolog`
+- `freshbump`
+- `fresqui`
+- `friendfeed`
+- `funp`
+- `fwisp`
+- `gabbr`
+- `gamespot`
+- `github`
+- `gmail`
+- `google`
+- `google_drive`
+- `google_hangout`
+- `google_photos`
+- `google_play`
+- `google_play_light`
+- `google_plus`
+- `grooveshark`
+- `hatena`
+- `html5`
+- `identi.ca`
+- `instagram`
+- `instapaper`
+- `ios`
+- `jamespot`
+- `java`
+- `joomla`
+- `jquery`
+- `json`
+- `json_2`
+- `last.fm`
+- `linkagogo`
+- `linkedin`
+- `livejournal`
+- `mail.ru`
+- `meetup`
+- `meneame`
+- `messenger`
+- `messenger_2`
+- `messenger_3`
+- `mind_body_green`
+- `mongodb`
+- `mxgraph.webicons`
+- `myspace`
+- `n4g`
+- `netlog`
+- `netvibes`
+- `netvouz`
+- `networkedblogs`
+- `newsvine`
+- `odnoklassniki`
+- `oknotizie`
+- `onedrive`
+- `oracle`
+- `paypal`
+- `phone`
+- `phonefavs`
+- `pinterest`
+- `plaxo`
+- `playfire`
+- `plurk`
+- `pocket`
+- `protopage`
+- `readernaut`
+- `reddit`
+- `rss`
+- `scoopit`
+- `scribd`
+- `segnalo`
+- `sina`
+- `sitejot`
+- `skype`
+- `skyrock`
+- `slashdot`
+- `sms`
+- `socialvibe`
+- `society6`
+- `sonico`
+- `soundcloud`
+- `sourceforge`
+- `sourceforge_2`
+- `spring.me`
+- `stackexchange`
+- `stackoverflow`
+- `startaid`
+- `startlap`
+- `steam`
+- `stumbleupon`
+- `stumpedia`
+- `technorati`
+- `translate`
+- `tumblr`
+- `tunein`
+- `twitter`
+- `two`
+- `typepad`
+- `viadeo`
+- `viber`
+- `viddler`
+- `vimeo`
+- `virb`
+- `vkontakte`
+- `wakoopa`
+- `weheartit`
+- `whatsapp`
+- `wix`
+- `wordpress`
+- `wordpress_2`
+- `xanga`
+- `xerpi`
+- `xing`
+- `yahoo`
+- `yahoo_2`
+- `yammer`
+- `yandex`
+- `yelp`
+- `yoolink`
+- `youmob`