docs: unify casing and replace path-as-text links across recent doc surfaces

Sweep recent (last ~5h) doc edits for two readability/uniformity issues:

- Replace 42 path-as-text links of the form '[/foo/bar](/foo/bar)' with
  descriptive labels derived from each target page's frontmatter title
  (e.g. '[Anthropic]', '[Token use and costs]', '[OpenAI-compatible
  endpoints]'). Affected files include gateway/troubleshooting,
  concepts/oauth, reference/session-management-compaction, and
  reference/transcript-hygiene.
- Sentence-case Title-Cased headings and link text in Related sections
  across codex-harness, model-providers, tools/plugin, sdk-runtime,
  sdk-setup, prompt-caching, ci, cli/config, google-meet, browser,
  rich-output-protocol, subagents, web/control-ui, while preserving
  brand and proper-noun capitalization (OpenAI, Codex, Chrome, Parallels,
  Z.AI, etc.).

docs/plugins/google-meet.md

@@ -158,7 +158,7 @@ the microphone/speaker path used by OpenClaw. For clean duplex audio, use
 separate virtual devices or a Loopback-style graph; a single BlackHole device is
 enough for a first smoke test but can echo.
 
-### Local Gateway + Parallels Chrome
+### Local gateway + Parallels Chrome
 
 You do **not** need a full OpenClaw Gateway or model API key inside a macOS VM
 just to make the VM own Chrome. Run the Gateway and agent locally, then run a