docs(copilot): document GitHub Copilot CLI in full

- New docs/copilot-integration.md in the shape of the other CLI guides: install and identity
  probe, authentication (keychain vs plain-text config.json, COPILOT_GITHUB_TOKEN), what Codeman
  wires up (Run button --yolo and its clamp, model, resume, continue, --name rule), BYOK custom
  endpoints, terminal behaviour (drag selection, wheel and touch), the codeman agent verbs
  (ready mark, read), plan usage, Docker, Remote SSH, what is deliberately not wired, known gaps.
- Agent-CLIs wiki: the eleven-modes table, a GitHub Copilot CLI section, the env prefix row, the
  feature-comparison rows and the status endpoint list.
- README, Home, FAQ, Core Concepts, Docker Cases, Remote SSH, Contributing, The Dashboard and
  Custom Model Endpoints: mode lists and counts; CLAUDE.md: stack line, SessionMode, prefixes,
  resolver list, external-CLI notes and the plan-usage source; api-reference MCP target wording;
  the env allowlist error message names COPILOT_*.

src/web/schemas.ts

@@ -259,7 +259,7 @@ const safeEnvOverridesSchema = z
     },
     {
       message:
-        'envOverrides contains blocked or disallowed env var keys. Only CLAUDE_CODE_*, OPENCODE_*, CODEX_*, GEMINI_*, GOOGLE_*, ANTIGRAVITY_*, PI_*, GROK_*, XAI_*, DSH_*, DEEPSEEK_*, OMP_* keys and CLAUDE_CONFIG_DIR are allowed.',
+        'envOverrides contains blocked or disallowed env var keys. Only CLAUDE_CODE_*, OPENCODE_*, CODEX_*, GEMINI_*, GOOGLE_*, ANTIGRAVITY_*, PI_*, GROK_*, XAI_*, DSH_*, DEEPSEEK_*, OMP_*, COPILOT_* keys and CLAUDE_CONFIG_DIR are allowed.',
     }
   );