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/ci.md

@@ -79,7 +79,7 @@ gh workflow run duplicate-after-merge.yml \
 | `android`                        | Android unit tests for both flavors plus one debug APK build                                 | Android-relevant changes             |
 | `test-performance-agent`         | Daily Codex slow-test optimization after trusted activity                                    | Main CI success or manual dispatch   |
 
-## Fail-Fast Order
+## Fail-fast order
 
 Jobs are ordered so cheap checks fail before expensive ones run: