docs: replace ampersand headings for stable Mintlify anchors

Per docs/CLAUDE.md, Mintlify anchor generation is brittle for headings
that contain em dashes, apostrophes, and ampersands. Normalize 9 H2
headings across docs/date-time.md, docs/pi.md, docs/platforms/{index,
macos, mac/webchat, mac/peekaboo}.md, docs/nodes/{images,audio}.md, and
docs/reference/AGENTS.default.md from `X & Y` to `X and Y` so anchors
do not collapse on entity decoding. Verified no inbound anchor references
to the renamed sections in the docs tree.

docs/nodes/audio.md

@@ -144,7 +144,7 @@ Note: Binary detection is best-effort across macOS/Linux/Windows; ensure the CLI
 }
 ```
 
-## Notes & limits
+## Notes and limits
 
 - Provider auth follows the standard model auth order (auth profiles, env vars, `models.providers.*.apiKey`).
 - Groq setup details: [Groq](/providers/groq).

docs/nodes/images.md

@@ -51,7 +51,7 @@ The WhatsApp channel runs via **Baileys Web**. This document captures the curren
   - If the active primary image model already supports vision natively, OpenClaw skips the `[Image]` summary block and passes the original image to the model instead.
 - By default only the first matching image/audio/video attachment is processed; set `tools.media.<cap>.attachments` to process multiple attachments.
 
-## Limits & Errors
+## Limits and errors
 
 **Outbound send caps (WhatsApp web send)**