refactor: pilot /cnc-logs as a skill with inline !block

[claylo]

The original /cnc-logs implementation was a two-piece trick: register a
UserPromptSubmit hook that fires on every prompt, guard it inside the
script with a prompt-prefix check, and use commands/cnc-logs.md to tell
Claude "the output is above." That shape spawned several of the bugs
this session has been untangling:

• UserPromptSubmit matchers are silently ignored, so the hook fired on
  every prompt and filtering had to happen inside the script.
• The script's substring guard didn't match the plugin-namespaced
  /cnc: form and needed a second fix.
• The "rendered above" framing relied on an ordering contract between
  hook stdout and command-markdown expansion that isn't documented.
  Per slash-commands.md lines 26 and 378-406, the correct shape is a skill
  that runs the log script at prompt-expansion time via an inline !block.
  Each !<command> executes before Claude sees anything, and its stdout
  is substituted into the skill content, so the fully-rendered prompt
  contains the actual log dashboard plus the summary instruction together.
  No matcher, no guard, no ordering assumption.
  Pilot the pattern on /cnc-logs only; /cncflip stays on the old
  UserPromptSubmit pattern until this shape is proven in anger.
  Changes:
• Add skills/cnc-logs/SKILL.md with disable-model-invocation,
  argument-hint for autocomplete, allowed-tools: Bash, and an inline

  $ARGUMENTS.
  

• Strip hooks/cnc-logs.sh of its stdin+jq prompt parsing and
  prompt-prefix guard. It now accepts positional args directly via
  args="$*", which works both from the skill's !block and from any
  direct invocation for debugging.
• Remove the cnc-logs.sh UserPromptSubmit registration from
  hooks/hooks.json. The toggle-hook.sh registration stays.
• Delete commands/cnc-logs.md. The skill supersedes it under the same
  /cnc-logs name and the docs explicitly say skills take precedence
  over commands of the same name.
  Verification: bash hooks/cnc-logs.sh (summary) and hooks/cnc-logs.sh
  rustfmt (drill-down) both render correctly from a direct call with no
  stdin piping. hooks.json parses clean. shellspec full suite still at
  46/46 — toggle_hook_spec coverage unchanged.