feat(honcho): context injection overhaul, 5-tool surface, cost safety, session isolation (#10619)

Salvaged from PR #9884 by erosika. Cherry-picked plugin changes onto
current main with minimal core modifications.

Plugin changes (plugins/memory/honcho/):
- New honcho_reasoning tool (5th tool, splits LLM calls from honcho_context)
- Two-layer context injection: base context (summary + representation + card)
  on contextCadence, dialectic supplement on dialecticCadence
- Multi-pass dialectic depth (1-3 passes) with early bail-out on strong signal
- Cold/warm prompt selection based on session state
- dialecticCadence defaults to 3 (was 1) — ~66% fewer Honcho LLM calls
- Session summary injection for conversational continuity
- Bidirectional peer targeting on all 5 tools
- Correctness fixes: peer param fallback, None guard on set_peer_card,
  schema validation, signal_sufficient anchored regex, mid->medium level fix

Core changes (~20 lines across 3 files):
- agent/memory_manager.py: Enhanced sanitize_context() to strip full
  <memory-context> blocks and system notes (prevents leak from saveMessages)
- run_agent.py: gateway_session_key param for stable per-chat Honcho sessions,
  on_turn_start() call before prefetch_all() for cadence tracking,
  sanitize_context() on user messages to strip leaked memory blocks
- gateway/run.py: skip_memory=True on 2 temp agents (prevents orphan sessions),
  gateway_session_key threading to main agent

Tests: 509 passed (3 skipped — honcho SDK not installed locally)
Docs: Updated honcho.md, memory-providers.md, tools-reference.md, SKILL.md

Co-authored-by: erosika <erosika@users.noreply.github.com>

gateway/run.py

@@ -3739,6 +3739,7 @@ class GatewayRunner:
                                     model=_hyg_model,
                                     max_iterations=4,
                                     quiet_mode=True,
+                                    skip_memory=True,
                                     enabled_toolsets=["memory"],
                                     session_id=session_entry.session_id,
                                 )
@@ -6221,6 +6222,7 @@ class GatewayRunner:
                 model=model,
                 max_iterations=4,
                 quiet_mode=True,
+                skip_memory=True,
                 enabled_toolsets=["memory"],
                 session_id=session_entry.session_id,
             )
@@ -8588,6 +8590,7 @@ class GatewayRunner:
                     session_id=session_id,
                     platform=platform_key,
                     user_id=source.user_id,
+                    gateway_session_key=session_key,
                     session_db=self._session_db,
                     fallback_model=self._fallback_model,
                 )