docs(upstream): add durable intelligence registry

[blakinio]

Purpose

Persist OTClient upstream/fork audit state in Git instead of relying on chat history.

Delivered

• docs/agents/programs/OTCLIENT_UPSTREAM_INTELLIGENCE.md with the 2026-07-17 baseline, current repository/fork tips, candidate statuses, safety rules and update workflow;
• artifacts/upstream/otclient/candidates.json schema version 1 with 26 tracked P0/P1/P2 candidates, deduplication/watch entries and audit history;
• discovery routing from docs/agents/README.md;
• bounded task record with overlap and validation evidence.

Current pinned state

• target blakinio/otclient:main: ca78b71397cd2196ab841144c27275d0462902d7;
• upstream opentibiabr/otclient:main: e1a1ff150332b8879c91d46d8dc1402e78af9c3e;
• common baseline: bdea0b23b4a738809d698cb7e4f88a299dd6bffc.

Boundaries

• documentation/data only;
• no runtime, protocol, client-assets, UI or test behavior change;
• no external repository writes;
• candidate monitoring does not authorize implementation;
• CHANGELOG.md is deliberately untouched because active PR fix(assets): select release archives by client version #37 owns it.

Validation

• JSON content parsed before publication;
• branch diff is limited to the programme, registry, README route and task record;
• applicable exact-head GitHub checks are required before squash merge.

Task: OTC-20260726-upstream-intelligence-registry