Track Flue skill and refresh top-level docs

- Commit the vendored Flue SKILL.md under .agents/skills/flue and the
  .claude/skills/flue symlink plus skills-lock.json entry.
- Rewrite AGENTS.md down to the repo's actual conventions and expand
  README.md with daemon/TUI/dev script notes.

skills-lock.json

@@ -25,6 +25,12 @@
       "skillPath": "cron-jobs/SKILL.md",
       "computedHash": "298eb217e7009f128416a97a172ccaa9325e0d3c2ef3d29fc4b894011ebc539d"
     },
+    "flue": {
+      "source": "withastro/flue",
+      "sourceType": "github",
+      "skillPath": "skills/flue/SKILL.md",
+      "computedHash": "c9ccd18babb912f52037e42b674a6c0de09d0459331000b11be98d31687f35fd"
+    },
     "rivetkit": {
       "source": "rivet-dev/skills",
       "sourceType": "github",