fork: scaling fixes (index-only context + chunking + model wiring)

Fixes upstream issues #3/#5/#9 (whole-wiki in every prompt) and adds
large-log chunking. Addresses the audit's P1 scaling findings (C1),
the chunking requirement operator added on top, C8 explicit model
wiring across all LLM call sites, and D3 single-event-loop refactor.

## compile.py

- **Index-only context.** The `existing_articles_context` concatenation
  of every wiki article has been removed from the prompt. Instead the
  LLM receives only the index + schema + daily log and uses the Read
  tool (already in allowed_tools) to fetch specific articles it decides
  are relevant. Prompt size stays bounded regardless of KB growth —
  upstream's 250K-token prompts past ~100 articles are gone.

- **Chunking.** `_split_log_into_chunks()` splits oversized daily logs
  along `### ` section boundaries. Threshold MAX_LOG_CHARS_PER_CHUNK
  (default 100K chars ≈ 25K tokens, configurable via
  MEMORIA_MAX_LOG_CHARS). Chunks compile via separate LLM calls that
  naturally merge through Edit on shared files. Oversized single
  sections emit as their own chunks rather than splitting mid-thought.

- **Atomic state on chunked compile.** State is only written after
  ALL chunks succeed — partial-failure leaves the log flagged as
  uncompiled in state.json so the next run retries it cleanly. Was
  already correct for single-chunk logs (early return on SDK error)
  and now correct for multi-chunk too.

- **Explicit model.** `model=COMPILE_MODEL` passed to
  ClaudeAgentOptions. Default "sonnet"; override via
  MEMORIA_COMPILE_MODEL env var.

- **D3: single asyncio.run.** The per-file `asyncio.run()` in the
  compile loop is replaced with one outer call wrapping `_compile_all`.
  Avoids repeated event-loop setup/teardown and matches the pattern
  used for async resources in the SDK.

## query.py

- **Index-only context.** `read_all_wiki_content()` replaced with
  `read_wiki_index()`. The LLM reads the index and uses its Read tool
  to fetch specific articles. Same rationale as compile.py — keeps
  prompt size bounded and cost predictable.

- **Explicit model.** `model=QUERY_MODEL`, default "sonnet", override
  via MEMORIA_QUERY_MODEL.

## lint.py

- **C9: skip qa/sources in missing-backlink check.** Articles under
  qa/ or sources/ no longer trigger a suggestion that every referenced
  concept should backlink to them. Concepts aren't expected to link
  back to every Q&A that mentions them — doing so would drown real
  relationships.

- **Alias-aware backlink detection.** Uses `extract_wikilinks()` to
  parse the target's link list so `[[concepts/foo|Display]]` forms
  count as valid backlinks (previously required exact `[[foo]]` match,
  causing false positives on aliased forms).

- **Explicit model.** `model=LINT_MODEL` in check_contradictions call,
  default "sonnet", override via MEMORIA_LINT_MODEL.

## Verified

- Chunking: 120K-char 3-section log splits into 80K + 40K, reconstructs
  byte-exact. Oversized single section (150K) emits as its own chunk.
  Small log (<100K) returns as single chunk.
- All patched modules import cleanly with expected config values.
- compile_daily_log / query.run_query / flush.maybe_trigger_compilation
  / lint.check_missing_backlinks all callable post-patch.

scripts/lint.py

@@ -13,9 +13,15 @@ from __future__ import annotations
 
 import argparse
 import asyncio
+import os
 from pathlib import Path
 
 from config import KNOWLEDGE_DIR, REPORTS_DIR, now_iso, today_iso
+
+# Contradiction-check model. Kept as Sonnet for reasoning quality; override
+# via MEMORIA_LINT_MODEL (e.g. to use a cheaper model for structural runs
+# that happen to include the LLM check).
+LINT_MODEL = os.environ.get("MEMORIA_LINT_MODEL", "sonnet")
 from utils import (
     count_inbound_links,
     extract_wikilinks,
@@ -105,20 +111,36 @@ def check_stale_articles() -> list[dict]:
 
 
 def check_missing_backlinks() -> list[dict]:
-    """Check for asymmetric links: A links to B but B doesn't link to A."""
+    """Check for asymmetric links: A links to B but B doesn't link to A.
+
+    Skips any source or target under `qa/` or `sources/`: Q&A articles
+    intentionally reference concepts without requiring a reciprocal link
+    (concepts would otherwise accumulate a backlink per question, which
+    drowns real relationships). Also handles pipe-aliased wikilinks via
+    the alias-aware extract_wikilinks helper.
+    """
     issues = []
+    # Aliased/nested variants of the source link that should count as a
+    # valid backlink on the target side: bare slug, and pipe-aliased form.
     for article in list_wiki_articles():
         content = article.read_text(encoding="utf-8")
         rel = article.relative_to(KNOWLEDGE_DIR)
-        source_link = str(rel).replace(".md", "").replace("\\", "/")
+        rel_str = str(rel).replace("\\", "/")
+
+        # Skip one-way source categories.
+        if rel_str.startswith("qa/") or rel_str.startswith("sources/"):
+            continue
+
+        source_link = rel_str.replace(".md", "")
 
         for link in extract_wikilinks(content):
-            if link.startswith("daily/"):
+            if link.startswith("daily/") or link.startswith("qa/") or link.startswith("sources/"):
                 continue
             target_path = KNOWLEDGE_DIR / f"{link}.md"
             if target_path.exists():
                 target_content = target_path.read_text(encoding="utf-8")
-                if f"[[{source_link}]]" not in target_content:
+                target_backlinks = extract_wikilinks(target_content)
+                if source_link not in target_backlinks:
                     issues.append({
                         "severity": "suggestion",
                         "check": "missing_backlink",
@@ -185,6 +207,7 @@ Do NOT output anything else - no preamble, no explanation, just the formatted li
             prompt=prompt,
             options=ClaudeAgentOptions(
                 cwd=str(ROOT_DIR),
+                model=LINT_MODEL,
                 allowed_tools=[],
                 max_turns=2,
             ),