Add minimax media skills and ABOUT.md; end-session/reflect updates; MiniMax-M3.1-Flash note in minimax-mesh

Includes the minimax-mesh switch to M3.1-Flash-Preview at effort low,
README/reflection-state refresh, and removal of two old session logs.

skills/minimax-music/SKILL.md

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+---
+name: minimax-music
+description: >
+  Generate music or a song from a prompt (and optional lyrics) via the MiniMax
+  music API. Use when the user wants music, a beat, a soundtrack, a theme song,
+  background music, or a melody. Trigger on phrases like "make a song",
+  "compose music", "background music", "theme tune", "lo-fi beat".
+allowed-tools: Bash(minimax-gen music *), Bash(minimax-gen --help), Bash(mkdir *), Bash(ls *), Bash(test *), Bash(file *), Read
+---
+
+# /minimax-music — Music Generation
+
+Generate a music track via the MiniMax music API. Lyrics are optional.
+
+## CLI
+
+```bash
+# Instrumental
+minimax-gen music --prompt "epic, 120 bpm, brass, strings" --instrumental \
+  --out /tmp/theme.mp3
+
+# With lyrics (read from a file)
+minimax-gen music --lyrics @lyrics.txt --prompt "indie folk, warm acoustic" \
+  --out /tmp/song.mp3
+
+# Auto-generated lyrics from the prompt
+minimax-gen music --prompt "a love song with a slow build" --lyrics-optimizer \
+  --out /tmp/love.mp3
+```
+
+The CLI is at `~/dev/claude/gamedev/minimax-gen/bin/minimax-gen`.
+
+## Choose a model
+
+| Model | Use |
+|---|---|
+| `music-3.0` (default) | latest, paid (may queue 5+ min during peak) |
+| `music-3.0-free` | free tier, 3 RPM, ~40s typical |
+| `music-2.6` / `music-2.6-free` | previous gen |
+| `music-cover` | needs `--audio-url` or `--audio-base64` reference |
+
+Tip: scripts and smoke tests should use `music-3.0-free` to avoid burning credits.
+
+## Structure tags for lyrics
+
+```
+[Intro]
+[Verse 1]
+[Pre Chorus]
+[Chorus]
+[Interlude]
+[Bridge]
+[Outro]
+[Inst]
+```
+
+## Timeouts
+
+Music can take up to 5 minutes. Default `--timeout` is 600s. Bump it for longer
+tracks or when the queue is busy.
+
+## After the call
+
+1. Show the path written and the `trace_id` from the sidecar `.meta.json`.
+2. Note the duration (`duration_ms`) and size so the user knows what to expect.
+3. Don't dump the meta JSON into chat — point at the file.
+
+## Never do
+
+- Never echo, log, or commit the contents of `~/.claude-secrets/minimax-auth-token`.
+- Never pass the token on a command line.
+
+## Reference
+
+Full option list: `minimax-gen music --help`