feat: fold project-scoped memories into context pack

The retrieval-quality review on 2026-04-11 found that active
project/knowledge/episodic memories never reached the pack: only
Trusted Project State and identity/preference memories were being
assembled. Reinforcement bumped confidence on memories that had
no retrieval outlet, so the reflection loop was half-open.

This change adds a third memory tier between identity/preference
and retrieved chunks:

- PROJECT_MEMORY_BUDGET_RATIO = 0.15
- Memory types: project, knowledge, episodic
- Only populated when a canonical project is in scope — without
  a project hint, project memories stay out (cross-project bleed
  would rot the signal)
- Rendered under a dedicated "--- Project Memories ---" header
  so the LLM can distinguish it from the identity/preference band
- Trim order in _trim_context_to_budget: retrieval → project
  memories → identity/preference → project state (most recently
  added tier drops first when budget is tight)

get_memories_for_context gains header/footer kwargs so the two
memory blocks can be distinguished in a single pack without a
second helper.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/atocore/memory/service.py

@@ -344,6 +344,8 @@ def get_memories_for_context(
     memory_types: list[str] | None = None,
     project: str | None = None,
     budget: int = 500,
+    header: str = "--- AtoCore Memory ---",
+    footer: str = "--- End Memory ---",
 ) -> tuple[str, int]:
     """Get formatted memories for context injection.
 
@@ -351,15 +353,16 @@ def get_memories_for_context(
 
     Budget allocation per Master Plan section 9:
       identity: 5%, preference: 5%, rest from retrieval budget
+
+    The caller can override ``header`` / ``footer`` to distinguish
+    multiple memory blocks in the same pack (e.g. identity/preference
+    vs project/knowledge memories).
     """
     if memory_types is None:
         memory_types = ["identity", "preference"]
 
     if budget <= 0:
         return "", 0
-
-    header = "--- AtoCore Memory ---"
-    footer = "--- End Memory ---"
     wrapper_chars = len(header) + len(footer) + 2
     if budget <= wrapper_chars:
         return "", 0