fix(spec): prefix bundle-relative resource paths with leading slash

[Vedant021004]

Summary

Fixes #29.

SPEC.md §6.2 defines a bundle-relative path as beginning with /, distinguishing it from concept-relative paths (../\ or ./). However, the reference bundle \�undles/acme_retail\ and the spec examples in §6.3, §10.2, and §10.3 wrote bundle-relative resources without a leading slash.

This caused ambiguity for consumers implementing §6.2, which would resolve these paths relative to the containing concept subdirectory instead of the bundle root.

Changes

1. SPEC.md:
   • §6.3: Updated references path to /references/attesters/revenue.py.
   • §10.2: Updated executor/attester resources to /references/skills/run-on-bq.md\ and /references/attesters/revenue.py.
   • §10.3: Updated computation path to /references/computations/lib/revenue.sql.
2. bundles/acme_retail:
   • Prefixed 12 path-valued frontmatter fields in computations, metrics, and tables with /.

Verification

• Full test suite passes: \pytest\ -> 39 passed in 6.36s.
• Signed-off-by included on commit for Google CLA compliance.

[google-cla]

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

[Vedant021004]

I signed it!