chore: upgrade to fab-kit 2.7.1 + apply 2.6.6→2.7.0 migration

[sahil-noon]

Summary

Upgrades this repo to fab-kit 2.7.1 and applies the 2.6.6 → 2.7.0 version migration.

Two one-line changes:

File	Change
fab/project/config.yaml	fab_version: 2.6.6 → 2.7.1
fab/.kit-migration-version	2.6.6 → 2.7.0

Migration 2.6.6 → 2.7.0 — two-column memory index re-baseline

The 2.7.0 migration drops the Last Updated column from docs/memory/**/index.md (the index is now a pure function of content, no git dates — branch-independent and idempotent).

Applied via /fab-setup migrations:

• Pre-checks passed — binary emits two-column output; docs/memory/ present.
• Re-baseline was a no-op — the memory tree was already two-column (regenerated during the ugde dev work that introduced 2.7.0). fab memory-index reported "already up to date" with a no-op diff, so there is no docs/memory/ churn in this PR.
• All five verification steps passed, including fab memory-index --check exit 0 and byte-stability on re-run.
• src/kit/VERSION already reads 2.7.1, so the migration's "bump kit VERSION" step was already satisfied (no downgrade).

Residual

After this migration the marker reads 2.7.0 while the engine is 2.7.1 — there is no 2.7.0 → 2.7.1 migration file, so the tail is a no-op that fab upgrade-repo stamps to engine version on its next run.

🤖 Generated with Claude Code