docs: typography hygiene across 6 pages

Replaced 66 typography characters (curly quotes, apostrophes, em/en
dashes, non-breaking hyphens) with ASCII equivalents per
docs/CLAUDE.md heading and content hygiene rules.

- docs/channels/mattermost.md: 12 chars
- docs/tools/plugin.md: 11 chars
- docs/providers/xai.md: 11 chars
- docs/plugins/building-plugins.md: 11 chars
- docs/concepts/streaming.md: 11 chars
- docs/concepts/model-providers.md: 11 chars

docs/channels/mattermost.md

@@ -361,7 +361,7 @@ When a user clicks a button:
 <AccordionGroup>
   <Accordion title="Implementation notes">
     - Button callbacks use HMAC-SHA256 verification (automatic, no config needed).
-    - Mattermost strips callback data from its API responses (security feature), so all buttons are removed on click — partial removal is not possible.
+    - Mattermost strips callback data from its API responses (security feature), so all buttons are removed on click - partial removal is not possible.
     - Action IDs containing hyphens or underscores are sanitized automatically (Mattermost routing limitation).
 
   </Accordion>
@@ -391,7 +391,7 @@ External scripts and webhooks can post buttons directly via the Mattermost REST
       {
         actions: [
           {
-            id: "mybutton01", // alphanumeric only — see below
+            id: "mybutton01", // alphanumeric only - see below
             type: "button", // required, or clicks are silently ignored
             name: "Approve", // display label
             style: "primary", // optional: "default", "primary", "danger"
@@ -416,11 +416,11 @@ External scripts and webhooks can post buttons directly via the Mattermost REST
 **Critical rules**
 
 1. Attachments go in `props.attachments`, not top-level `attachments` (silently ignored).
-2. Every action needs `type: "button"` — without it, clicks are swallowed silently.
-3. Every action needs an `id` field — Mattermost ignores actions without IDs.
+2. Every action needs `type: "button"` - without it, clicks are swallowed silently.
+3. Every action needs an `id` field - Mattermost ignores actions without IDs.
 4. Action `id` must be **alphanumeric only** (`[a-zA-Z0-9]`). Hyphens and underscores break Mattermost's server-side action routing (returns 404). Strip them before use.
 5. `context.action_id` must match the button's `id` so the confirmation message shows the button name (e.g., "Approve") instead of a raw ID.
-6. `context.action_id` is required — the interaction handler returns 400 without it.
+6. `context.action_id` is required - the interaction handler returns 400 without it.
 
 </Warning>
 
@@ -467,7 +467,7 @@ context = {**ctx, "_token": token}
   <Accordion title="Common HMAC pitfalls">
     - Python's `json.dumps` adds spaces by default (`{"key": "val"}`). Use `separators=(",", ":")` to match JavaScript's compact output (`{"key":"val"}`).
     - Always sign **all** context fields (minus `_token`). The gateway strips `_token` then signs everything remaining. Signing a subset causes silent verification failure.
-    - Use `sort_keys=True` — the gateway sorts keys before signing, and Mattermost may reorder context fields when storing the payload.
+    - Use `sort_keys=True` - the gateway sorts keys before signing, and Mattermost may reorder context fields when storing the payload.
     - Derive the secret from the bot token (deterministic), not random bytes. The secret must be the same across the process that creates buttons and the gateway that verifies.
 
   </Accordion>
@@ -477,7 +477,7 @@ context = {**ctx, "_token": token}
 
 The Mattermost plugin includes a directory adapter that resolves channel and user names via the Mattermost API. This enables `#channel-name` and `@username` targets in `openclaw message send` and cron/webhook deliveries.
 
-No configuration is needed — the adapter uses the bot token from the account config.
+No configuration is needed - the adapter uses the bot token from the account config.
 
 ## Multi-account
 
@@ -531,8 +531,8 @@ Mattermost supports multiple accounts under `channels.mattermost.accounts`:
 
 ## Related
 
-- [Channel Routing](/channels/channel-routing) — session routing for messages
-- [Channels Overview](/channels) — all supported channels
-- [Groups](/channels/groups) — group chat behavior and mention gating
-- [Pairing](/channels/pairing) — DM authentication and pairing flow
-- [Security](/gateway/security) — access model and hardening
+- [Channel Routing](/channels/channel-routing) - session routing for messages
+- [Channels Overview](/channels) - all supported channels
+- [Groups](/channels/groups) - group chat behavior and mention gating
+- [Pairing](/channels/pairing) - DM authentication and pairing flow
+- [Security](/gateway/security) - access model and hardening