fix(skills): use python3 and inject skill directory path into prompt

- SKILL.md: python → python3 (macOS has no `python` binary)
- skills/index.ts: inject skill directory path so agent can resolve
  relative paths like scripts/recalc.py to absolute paths

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/core/src/agent/skills/index.ts

@@ -5,6 +5,7 @@
  * Compatible with OpenClaw/AgentSkills specification
  */
 
+import { dirname } from "path";
 import type { Skill, SkillManagerOptions, SkillsConfig, SkillCommandSpec, SkillInvocationResult } from "./types.js";
 import { loadAllSkills, getProfileSkillsDir, initializeManagedSkills, getManagedSkillsDir } from "./loader.js";
 import {
@@ -332,6 +333,11 @@ export class SkillManager {
         parts.push(`## ${emoji} ${name} (${id})`);
         parts.push(`${desc}\n`);
 
+        // Include skill directory path so the agent can resolve relative paths
+        // (e.g., scripts/recalc.py → /absolute/path/to/skill/scripts/recalc.py)
+        const skillDir = dirname(skill.filePath);
+        parts.push(`**Skill directory**: \`${skillDir}\`\n`);
+
         // Include full instructions
         if (skill.instructions) {
           parts.push(skill.instructions);

skills/xlsx/SKILL.md

@@ -151,7 +151,7 @@ This applies to ALL calculations - totals, percentages, ratios, differences, etc
 4. **Save**: Write to file
 5. **Recalculate formulas (MANDATORY IF USING FORMULAS)**: Use the scripts/recalc.py script
    ```bash
-   python scripts/recalc.py output.xlsx
+   python3 scripts/recalc.py output.xlsx
    ```
 6. **Verify and fix any errors**:
    - The script returns JSON with error details
@@ -224,12 +224,12 @@ wb.save('modified.xlsx')
 Excel files created or modified by openpyxl contain formulas as strings but not calculated values. Use the provided `scripts/recalc.py` script to recalculate formulas:
 
 ```bash
-python scripts/recalc.py <excel_file> [timeout_seconds]
+python3 scripts/recalc.py <excel_file> [timeout_seconds]
 ```
 
 Example:
 ```bash
-python scripts/recalc.py output.xlsx 30
+python3 scripts/recalc.py output.xlsx 30
 ```
 
 The script: