passepartout: v0.5.0 File Reorganization

Extract non-core fragments using self-repair criterion:
- core-context -> symbolic-awareness (224 lines, fboundp guards in think())
- heartbeat generation -> symbolic-events (renamed events-start-heartbeat)

Rename 23 files for clarity and new naming scheme:
- 6 core: core-package, core-transport, core-pipeline,
          core-perceive, core-reason, core-act
- 13 system: symbolic-*, neuro-*, embedding-*, channel-shell
- 4 gateway: channel-cli, channel-tui-*, channel-tui-state

Utility relocations:
- markdown-strip -> programming-markdown
- plist-keywords-normalize -> programming-lisp
- cognitive-tool-prompt -> programming-tools
- VAULT-MEMORY -> security-vault
- Merge *backend-registry* into *probabilistic-backends*

Split gateway-messaging into channel-telegram/channel-signal/
channel-discord/channel-slack (4 independent skills)

Delete dead system-model.lisp (16-line wrapper)

Document self-repair criterion in DESIGN_DECISIONS

Version bump: 0.4.3 -> 0.5.0

docs/DESIGN_DECISIONS.org

@@ -440,4 +440,6 @@ The critical risk is implementation: achieving the retrieval precision, Dispatch
 
 5. *Competitor evolution.* Sparse retrieval is not patentable. Claude Code, Copilot, and others will implement similar mechanisms. The architectural advantage is real but finite in duration. The deterministic safety gate is the harder-to-replicate differentiator.
 
+6. *The self-repair criterion.* "What belongs in core?" is decided by a single test: if this file is corrupted, can the agent fix it without human help? Corrupted core = dead brain, dead hands, or unreachable. Corrupted skill = degraded but self-repairable. If the agent has tools, identity, and user input, it can reason about missing awareness, edit the corrupted source file, reload the skill, and continue. If it loses its own reasoning loop, it has no way to self-diagnose. This is why context assembly and heartbeat generation were extracted to skills in v0.5.0 — the agent can detect their absence and reload them. The core contracts to the absolute minimum needed for self-repair: the pipeline, the memory, the transport, and the skill loader.
+