Fix dead docs/ links in packages/sdk/README.md

[toon-backlog-bot]

Summary

• packages/sdk/README.md linked to ../../docs/protocol.md and ../../docs/sdk-guide.md, relative paths that have never existed in this repo.
• Per this repo's CLAUDE.md, shared docs live in toon-protocol/toon-meta, not here — replaced both dead relative links with absolute links into that repo (preserving the #ilp-address-hierarchy anchor on the protocol.md link).
• Added an empty changeset (.changeset/issue-63-fix-sdk-readme-doc-links.md) since this is a docs-only change with no package version bump.

Closes #63

Verification

• grep -n '\.\./\.\./docs' packages/sdk/README.md → no matches (was 2 before the fix).
• devbox is not available in this sandbox, so verification ran directly per the repo's documented commands instead of via the pinned devbox shell (noted deviation):
  • pnpm install — succeeded.
  • pnpm -r build — succeeded (both @toon-protocol/core and @toon-protocol/sdk).
  • pnpm -r test — has pre-existing failures unrelated to this change (3 in packages/core/src/compose.test.ts, 50 in packages/sdk/src/workflow-orchestrator.test.ts and others). Confirmed identical failures reproduce on main with this change stashed out, so they predate this PR and are out of scope for a docs-only fix.

🤖 Generated with Claude Code

[ALLiDoizCode]

Reviewed the diff (packages/sdk/README.md + new changeset).

Checks performed:

• Confirmed via git log --all -- docs/ that no docs/ directory has ever existed in this repo, so the old ../../docs/protocol.md and ../../docs/sdk-guide.md links were genuinely dead.
• Verified both replacement targets exist in toon-protocol/toon-meta: docs/protocol.md (with an ## ILP Address Hierarchy heading matching the preserved #ilp-address-hierarchy anchor) and docs/sdk-guide.md.
• Grepped the whole repo for other docs/protocol.md / docs/sdk-guide.md references — these were the only two occurrences, so nothing was missed.
• Changeset uses the empty-frontmatter format (---\n---), correct for a docs-only change with no package version bump, consistent with .changeset/config.json.
• PR title/body accurately match the diff (2 additions/2 deletions in README, +4 new changeset file) — no metadata corrections needed.
• The build check is currently failing, but it's packages/core/src/compose.test.ts (bootstrap peer-count assertions) — unrelated to this diff, which only touches packages/sdk/README.md and .changeset/. Cross-checked recent CI runs on main: the same suite passed 56/56 on the last main run, so this looks like pre-existing flakiness in that test rather than something introduced here, matching what the PR description already discloses.

No blocking issues. LGTM.