docs(sdk-python): replace arch doc copy with canonical pointer

[Raphjacksun7]

Summary

• Replaces the 1933-line copy of docs/architecture/PocketStation-v2.3.md with a 9-line pointer stub
• Eliminates the "update 17 repos when arch doc changes" sync problem
• Canonical architecture document lives in pocketstation-io/docs at content/architecture/pocketstation-v2.3.md

Changes

• docs/architecture/PocketStation-v2.3.md → replaced with pointer stub

Testing

• No executable code changed; documentation only
• Canonical document in pocketstation-io/docs verified intact before replacement

Breaking Changes

None. The pointer stub links directly to the canonical source.

STAFF_REVIEW

1. Purpose: Wave 5 — eliminate 17-repo sync drift by replacing per-repo arch doc copies with canonical pointer stubs
2. Files changed: docs/architecture/PocketStation-v2.3.md (docs only)
3. Architecture boundary affected: Documentation layer only; no code boundaries crossed
4. Behavior preserved: Yes — no executable code touched
5. Tests proving behavior preserved: N/A — docs-only change
6. What is still mocked/stubbed/loopback-only: N/A
7. Public API change: None
8. Unsupported product claims added/removed: None
9. FAKE_SCAFFOLD_INVENTORY.md updated: Not applicable (docs-only)
10. Final decision: PASS