fix(tools): scope session_search to current gateway chat

[the3asic]

Summary

Fix session_search gateway scoping so Discord/Telegram/etc. gateway turns default to the current chat/thread instead of profile-wide history.

Key pieces:

• persist a gateway recall/search scope key on session rows (scope_key) plus minimal routing metadata (origin_json)
• split recall scope from the in-memory gateway session_key, so group/channel sessions can remain per-user while recall searches the whole current channel/thread
• pass HERMES_RECALL_SCOPE_KEY through gateway contextvars, cached agents, API server, and tool execution paths
• make gateway current-scope failures fail closed instead of silently falling back to global search
• add schema v18 data migration to backfill v17 rows that accidentally stored the full per-user session key
• keep scope='all' as the explicit opt-out for profile-wide/global history
• hide internal routing metadata from dashboard session APIs

Verification

python -m py_compile hermes_state.py gateway/session.py tools/session_search_tool.py agent/tool_executor.py agent/agent_runtime_helpers.py run_agent.py gateway/run.py gateway/session_context.py

/home/the3asic/.hermes/hermes-agent/.venv/bin/python -m pytest \
  tests/test_hermes_state.py::TestSessionLifecycle::test_v18_migration_backfills_recall_scope_keys \
  tests/tools/test_session_search.py \
  tests/gateway/test_session_scope_persistence.py \
  tests/agent/test_session_search_scope_executor.py \
  tests/gateway/test_session_env.py \
  -q -o 'addopts='
# 80 passed, 7 warnings

/home/the3asic/.hermes/hermes-agent/.venv/bin/python -m pytest \
  tests/test_hermes_state.py \
  tests/hermes_state/test_get_anchored_view.py \
  tests/hermes_state/test_get_messages_around.py \
  -q -o 'addopts='
# 302 passed

git diff --check
/home/the3asic/.hermes/hermes-agent/.venv/bin/python scripts/check-windows-footguns.py --diff origin/main
# ✓ No Windows footguns found

Notes

A live dogfood DB was backed up before running the v18 migration, then migrated successfully:

• backup: ~/.hermes/backups/state-before-recall-scope-v18-20260621T214508.db
• migrated candidates: 3
• remaining unmigrated candidates: 0

[lkz-de]

One overlap note from rechecking nearby work: PR #57981 (fix(compression): preserve gateway origin on child sessions) looks like a distinct narrow bug fix rather than a duplicate of this PR.

My current read is:

• #57981 fixes metadata preservation for compression-created child sessions on the rotation fallback path in agent/conversation_compression.py
• #50030 handles broader current-chat / session_search recall scoping

The meaningful overlap looks operational rather than conceptual: both PRs currently add tests/gateway/test_session_scope_persistence.py.

So if both lanes move forward, I would expect a manual merge on that shared test file — the two versions cover different scenarios and should both survive intact — rather than a duplication issue in the production logic.