chore(skills): add sdk-sample-sync skill

[jackchuka]

What

Adds a Claude Code skill — sdk-sample-sync — that verifies and updates the hand-written @tailor-platform/sdk code samples in this repo against the currently published SDK, and keeps the companion source in tailor-platform/templates in sync.

.claude/skills/sdk-sample-sync/
├── SKILL.md                       # the workflow
└── scripts/verify-sdk-project.sh  # install → tailor-sdk generate → tsc, with cleanup

Why

docs/sdk/ is auto-synced from the SDK package (scripts/docs-sync + sdk-docs-sync CI), but the tutorials/guides are hand-typed and nothing regenerates them — so they silently rot when the SDK API changes. That's exactly what happened to the develop-from-scratch tutorial.

The skill captures the workflow used to fix it:

• Source of truth = the published package. npm pack @tailor-platform/sdk@latest, read its bundled docs/ + CHANGELOG.md. Don't trust memory.
• Verify empirically. Prove fixes against the runnable templates project via verify-sdk-project.sh (install → generate → typecheck, cleaning up untracked generated artifacts).
• Hunt silent failures. A snippet can compile and still be wrong — e.g. the webhook body: field type-checked but was silently dropped (requestBody: is the real field). The skill teaches the TS7031-probe to expose unrecognized field names.
• Lockstep updates. Edit the templates source and the docs prose together; open cross-linked draft PRs.

Notes

• Independent of the tutorial-fix PR (docs(develop-from-scratch): update tutorial for @tailor-platform/sdk #132) and the templates migration (chore(build-from-scratch): migrate SDK guide to @tailor-platform/sdk templates#107) — those are the worked example this skill generalizes from.
• verify-sdk-project.sh was smoke-tested against a templates step: install → generate → typecheck → PASS, working tree left clean.
• First skill in the repo; establishes .claude/skills/ (not gitignored).