fix: support marketing-based project layout in skills and runs

[canovars]

Closes #23

What

The CLI currently assumes that installed skills and squads always live at the project root:

• skills/
• squads/

That breaks repositories that organize work by department and use:

• marketing/skills/
• marketing/squads/

There is also a separate bug in runs: any directory under output/ is treated as a run, so folders like output/images/ and output/slides/ appear as false run entries.

This PR updates:

• src/skills.js
  Prefer marketing/skills/ for new installs when a project uses the department-based layout, but continue to read, update, and remove skills from both marketing/skills/ and legacy skills/ during migration.

• src/runs.js
  Prefer marketing/squads/, keep legacy squads/ run history visible during migration, de-duplicate identical run ids across both layouts, and ignore non-run output directories.

• src/init.js and src/update.js
  Print the actual installed skill path instead of always logging skills/....

• src/readme/README.md
  Document both root-based and department-based dashboard paths.

• tests/skills.test.js and tests/runs.test.js
  Add regression coverage for mixed-layout migration cases.

Why

• Keeps existing root-based projects working
• Supports department-based repositories without requiring root aliases
• Avoids hiding legacy installed skills or historical runs during partial migration
• Keeps CLI output and README instructions aligned with runtime behavior

How to test

1. Create a test project with:
   • marketing/skills/example-skill/SKILL.md
   • marketing/squads/example-squad/output/images/
   • marketing/squads/example-squad/output/slides/
2. Run npx opensquad skills
3. Run npx opensquad runs example-squad

Expected after patch:

• skills lists skills installed in marketing/skills/
• runs resolves marketing/squads/
• runs does not report images or slides as run ids

4. Add a mixed migration case:
   • keep an existing skill only in skills/legacy-skill/
   • keep an existing run only in squads/legacy-squad/output/<run-id>/
   • also create marketing/skills/ and marketing/squads/

Expected after patch:

• the legacy skill remains visible to npx opensquad skills
• legacy runs remain visible to npx opensquad runs
• identical run ids across both layouts are listed only once

5. Run node --test

Validation used locally

Validated locally against opensquad@0.1.15.

Results after patch:

• npx opensquad skills correctly lists installed skills from mixed root and marketing/ layouts
• npx opensquad runs instagram-leads resolves marketing/squads
• npx opensquad runs instagram-leads no longer treats images/ and slides/ as runs
• node --test passes locally with 138 tests

Notes

If you would prefer a more general configurable path mechanism instead of explicit marketing/... fallback, I can adapt the patch in a follow-up. This PR keeps the change intentionally narrow while preserving backward compatibility during migration.