refactor(skills): portable script paths via ${CLAUDE_SKILL_DIR}

Replace literal `.claude/skills/<owner>/...` paths in SKILL.md with the
`${CLAUDE_SKILL_DIR}` variable that Claude Code substitutes at invocation
time. Same-skill references become `${CLAUDE_SKILL_DIR}/<rest>`,
cross-skill references (erf-* → epf-*) become
`${CLAUDE_SKILL_DIR}/../<other>/<rest>`. All paths now wrapped in double
quotes to handle install locations with spaces.

This unblocks plugin-mode installation: literal `.claude/skills/...`
paths fail when the skill is loaded from `~/.claude/plugins/cache/...`
or from a personal `~/.claude/skills/` install. Drop-in mode continues
to work because Claude Code resolves the variable in all install scopes.

Verified via pilot:
- Project drop-in (cc-1c-skills repo)
- Personal `~/.claude/skills/cf-info/`
- Plugin via `/plugin marketplace add <local-path>`

Scope: 61 SKILL.md, 125 path replacements (8 cross-skill).
Scripts unchanged — they already use \$PSScriptRoot and ../<sibling>
patterns that resolve correctly under the bundled cache layout.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.claude/skills/mxl-info/SKILL.md

@@ -38,12 +38,12 @@ allowed-tools:
 ## Команда
 
 ```powershell
-powershell.exe -NoProfile -File .claude/skills/mxl-info/scripts/mxl-info.ps1 -TemplatePath "<путь>"
+powershell.exe -NoProfile -File "${CLAUDE_SKILL_DIR}/scripts/mxl-info.ps1" -TemplatePath "<путь>"
 ```
 
 Или по имени обработки/макета:
 ```powershell
-powershell.exe -NoProfile -File .claude/skills/mxl-info/scripts/mxl-info.ps1 -ProcessorName "<Имя>" -TemplateName "<Макет>" [-SrcDir "<каталог>"]
+powershell.exe -NoProfile -File "${CLAUDE_SKILL_DIR}/scripts/mxl-info.ps1" -ProcessorName "<Имя>" -TemplateName "<Макет>" [-SrcDir "<каталог>"]
 ```
 
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