feat: 16 pain points docs, configurable User-Agent (#155), fix hardcoded $HOME (#156)

- Add collapsible '16 Real Pain Points' section to all 30 READMEs
- Fix 5 files bypassing dataPaths.ts with hardcoded os.homedir() (closes #156)
- Add per-provider User-Agent env var overrides in base executor (closes #155)
- Sync .env and .env.example with 9 provider UA defaults
- Update CHANGELOG.md for v1.7.0

.env.example

@@ -130,6 +130,22 @@ GEMINI_CLI_OAUTH_CLIENT_SECRET=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
 # IFLOW_OAUTH_CLIENT_ID=
 IFLOW_OAUTH_CLIENT_SECRET=4Z3YjXycVsQvyGF1etiNlIBB4RsqSDtW
 
+# ─────────────────────────────────────────────────────────────────────────────
+# Provider User-Agent Overrides (optional — customize per-provider UA headers)
+# ─────────────────────────────────────────────────────────────────────────────
+# Format: {PROVIDER_ID}_USER_AGENT=custom-value
+# When set, overrides the default User-Agent header sent to that provider.
+# Useful when providers update versions or block old user-agents.
+CLAUDE_USER_AGENT=claude-cli/1.0.83 (external, cli)
+CODEX_USER_AGENT=codex-cli/0.92.0 (Windows 10.0.26100; x64)
+GITHUB_USER_AGENT=GitHubCopilotChat/0.26.7
+ANTIGRAVITY_USER_AGENT=antigravity/1.104.0 darwin/arm64
+KIRO_USER_AGENT=AWS-SDK-JS/3.0.0 kiro-ide/1.0.0
+IFLOW_USER_AGENT=iFlow-Cli
+QWEN_USER_AGENT=google-api-nodejs-client/9.15.1
+CURSOR_USER_AGENT=connect-es/1.6.1
+GEMINI_CLI_USER_AGENT=google-api-nodejs-client/9.15.1
+
 # API Key Providers (Phase 1 + Phase 4)
 # Add via Dashboard → Providers → Add API Key, or set here
 # DEEPSEEK_API_KEY=