chore: add AGENTS.md, helper scripts, codex templates, and CI

doc/agents/codex_prompt_templates.md

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+Codex Prompt Templates
+
+Note
+- Keep prompts concise and specific. Include before/after or small input→output examples when helpful.
+- Use the Task Template in AGENTS.md for clarity and a crisp definition of Done.
+
+Next Task Format (from ~/.claude)
+---
+Next: <what to do>
+Complexity: simple | medium | complex
+---
+
+Bugfix Prompt
+---
+Context
+- Problem: <symptoms and scope>
+- Repro: <steps/command>
+- Observed: <actual result>
+- Expected: <desired result>
+- Constraints / Non‑goals: <limits>
+
+Done When
+- scripts/check.sh passes; behavior verified via repro
+- Tests/docs updated if applicable
+---
+
+Small Feature Prompt
+---
+Context
+- Goal: <user‑visible behavior>
+- Entry points: <screens/routes/widgets>
+- Data/State impact: <provider/models/side effects>
+- Constraints / Non‑goals: <limits>
+
+Done When
+- Feature is reachable and works
+- scripts/check.sh passes; minimal tests if feasible
+---
+
+Refactor Prompt (No Behavior Change)
+---
+Context
+- Target: <files/modules>
+- Motivation: <readability/duplication/perf>
+- Safety: <no logic change; add tests if risky>
+
+Done When
+- Same behavior; cleaner structure
+- scripts/check.sh passes
+---
+
+UI Change Prompt
+---
+Context
+- Screen/Widget: <where>
+- Visual Goal: <what changes>
+- Theming/Adaptivity: <light/dark/platform>
+
+Done When
+- Visual change implemented; screenshots added in PR by human
+- scripts/check.sh passes
+---
+
+Code Review Aid
+---
+- Summarize intent and key diffs
+- Verify formatting, analysis, and tests pass
+- Flag risks; suggest targeted follow‑ups
+---
+