Add cashtag support for stock ticker discussions (#9689)

* Add cashtag support for stock ticker discussions

Display cashtags ($TICKER format) as clickable links with dedicated menu actions and search feed, alongside hashtags. Includes composer highlighting and proper formatting.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

* Fix cashtag search query to use # prefix

Cashtags need to be searched as "#$BTC" rather than just "$BTC" to work
with the search API.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Update @atproto/api to 0.18.14 with cashtag support

The updated package includes native CASHTAG_REGEX detection for stock
ticker symbols like $AAPL and $BTC.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* Fix todo, remove redundant validation

---------

Co-authored-by: Claude Haiku 4.5 <noreply@anthropic.com>
Co-authored-by: Eric Bailey <git@esb.lol>

src/view/com/composer/text-input/web/TagDecorator.ts

@@ -14,7 +14,11 @@
  * the facet-set.
  */
 
-import {TAG_REGEX, TRAILING_PUNCTUATION_REGEX} from '@atproto/api'
+import {
+  CASHTAG_REGEX,
+  TAG_REGEX,
+  TRAILING_PUNCTUATION_REGEX,
+} from '@atproto/api'
 import {Mark} from '@tiptap/core'
 import {type Node as ProsemirrorNode} from '@tiptap/pm/model'
 import {Plugin, PluginKey} from '@tiptap/pm/state'
@@ -28,6 +32,7 @@ function getDecorations(doc: ProsemirrorNode) {
       const regex = TAG_REGEX
       const textContent = node.textContent
 
+      // Detect hashtags
       let match
       while ((match = regex.exec(textContent))) {
         const [matchedString, __, tag] = match
@@ -52,6 +57,27 @@ function getDecorations(doc: ProsemirrorNode) {
           }),
         )
       }
+
+      // Detect cashtags
+      const cashtagRegex = new RegExp(CASHTAG_REGEX.source, 'gu')
+      while ((match = cashtagRegex.exec(textContent))) {
+        const [_fullMatch, leading, ticker] = match
+
+        if (!ticker) continue
+
+        // Calculate positions: leading char + $ + ticker
+        const matchedFrom = match.index + leading.length
+        const matchedTo = matchedFrom + 1 + ticker.length // +1 for $
+
+        const start = pos + matchedFrom
+        const end = pos + matchedTo
+
+        decorations.push(
+          Decoration.inline(start, end, {
+            class: 'autolink',
+          }),
+        )
+      }
     }
   })