What does this PR do?

Fixes honcho_profile(peer="user") returning an empty card even when Honcho has a populated peer card for the user. Two independent bugs combined to produce the symptom:

Bug 1 — Read path (related to #17124): get_peer_card() calls _fetch_peer_card(observer, target=user), which hits GET /peers/{observer}/card?target={user} — the observer's local card of the user. On self-hosted Honcho v3 this slot is empty unless writes also use it; the peer card lives on the user peer itself (GET /peers/{user}/card).

Fix: when the observer-target slot returns empty and a target exists, fall back to _fetch_peer_card(target) — the target peer's own card.

Bug 2 — Write path (related to #20729): set_peer_card() resolved only the target peer and called user_peer.set_card(card). The read path uses the assistant peer as observer, so writes and reads addressed different Honcho card scopes. honcho_profile(card=[...]) reported success while a subsequent honcho_profile() still returned empty.

Fix: align set_peer_card() with _resolve_observer_target() so it writes to assistant_peer.set_card(card, target=user_peer_id), matching the read side.

Both fixes together ensure reads and writes use the same scope, and the read-side fallback handles existing deployments where cards were written directly to the peer.

Related issues / PRs

• Related to fix(honcho): fallback to durable peer cards for profiles #17124 (read-path fallback, same symptom, different approach)
• Related to fix: align Honcho profile card writes #20729 (write-path alignment)
• Related to fix(honcho): restore profile fallback and backfill memory files #13375

Type of change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✅ Tests (adding or improving test coverage)

Changes made

• plugins/memory/honcho/session.py
  • get_peer_card: add fallback to target peer's own card when observer-target slot is empty
  • set_peer_card: use _resolve_observer_target so write scope matches read scope
• tests/honcho_plugin/test_session.py
  • test_get_peer_card_falls_back_to_target_peer_own_card: regression test for the read fallback
  • test_set_peer_card_uses_observer_target_in_ai_observe_others_mode: regression test for write alignment

Validation

python -m pytest tests/honcho_plugin/test_session.py -q -o 'addopts='
# 117 passed

python -m pytest tests/honcho_plugin/ -q -o 'addopts='
# 269 passed

ruff check plugins/memory/honcho/session.py tests/honcho_plugin/test_session.py
# All checks passed

Checklist

• I've read the Contributing Guide
• My commit messages follow Conventional Commits
• I searched for existing PRs and referenced them above
• My PR contains only changes related to this fix
• I've added tests for my changes
• I've run pytest tests/honcho_plugin and all tests pass
• I've run ruff check and all checks pass