refactor: extract tmux-launch-agent from implement-issue/setup-skills, overhaul PKM skills

- New common/misc/tmux-launch-agent skill with detect-agent script
  and agents-seed.md (moved from engineering/setup-skills)
- implement-issue simplified: delegates agent dispatch to
  tmux-launch-agent instead of inlining it
- setup-skills stripped of Section E (agent CLI config)
- New in-progress/agent-handoff skill using tmux-launch-agent
- PKM skills simplified: conversation-summary and pkm-curation
  rewritten with leaner process, crit streamlined
- knowledge-gardener removed (moved to common/in-progress/)
- All READMEs updated to match

common/misc/tmux-launch-agent/agents-seed.md

@@ -0,0 +1,44 @@
+# TMUX Launch Agent — Agent CLI Seed Data
+
+## Agents
+
+```yaml
+agents:
+  - name: pi
+    binary: pi
+    args: "@{prompt}"
+    description: "My primary agent harness. Accepts prompt file via {prompt}."
+
+  - name: opencode
+    binary: opencode
+    args: ""
+    description: "OpenCode agent. Pipes stdin via cat."
+    note: "Uses stdin piping: args must be empty, prompt via pipe."
+
+  - name: goose
+    binary: goose
+    args: ""
+    description: "Goose agent. Accepts prompt file via -i flag."
+    note: "Uses stdin piping: args must be empty, prompt via pipe."
+
+  - name: codex
+    binary: codex
+    args: "@{prompt}"
+    description: "OpenAI Codex. Accepts prompt file via {prompt}."
+
+  - name: claude
+    binary: claude
+    args: ""
+    description: "Anthropic Claude CLI. Pipes stdin via cat."
+    note: "Uses stdin piping: args must be empty, prompt via pipe."
+```
+
+## Field meanings
+
+| Field | Description |
+|-------|-------------|
+| `name` | Display name used in menus and `--agent` flag |
+| `binary` | Command name expected on PATH |
+| `args` | Static arguments appended after the binary. May include `{prompt}` which is substituted at invocation time with the absolute path to the prompt file. Empty string means stdin piping (prompt is piped via `cat`). |
+| `description` | Short human-readable description for the setup menu |
+| `note` | Optional additional context |