feat: add Aider chat history markdown normalizer

[mvanhorn]

What does this PR do?

Adds a _try_aider_md() parser to normalize.py that extracts user/assistant conversations from Aider's .aider.chat.history.md files. Aider uses #### headings for user messages with assistant responses as plain text between them.

Wired into the normalize() auto-detect chain before JSON parsing. Only activates for .md files with 2+ #### markers.

Partially addresses #59 (Aider was called out as "lowest-hanging fruit" in the issue).

How to test

pytest tests/test_normalize.py::test_aider_md -v

Or with a real Aider history file:

from mempalace.normalize import normalize
result = normalize(".aider.chat.history.md")
print(result[:500])

Checklist

• Tests pass (python -m pytest tests/ -v) - 102 tests pass
• No hardcoded paths
• Linter passes (ruff check .)

This contribution was developed with AI assistance (Codex).

[adv3nt3]

Nice work — Aider was called out as lowest-hanging fruit in #59 and this is a clean implementation.

A few concerns:

1. False positive risk on regular markdown files. Any .md file with 2+ #### headings will trigger the parser — CONTRIBUTING.md, CHANGELOG.md, API docs, etc. Aider's history file has a very specific name (.aider.chat.history.md). Checking the filename would be a much safer fingerprint:

if ext == ".md" and Path(filepath).name == ".aider.chat.history.md":

2. User messages can span multiple lines. In real Aider sessions, users sometimes paste multi-line code or context after the #### heading. The current parser treats everything after #### as assistant text until the next ####, which would split a multi-line user prompt and misattribute part of it as an assistant response.

3. No structural fingerprint. The other JSONL/JSON parsers (Codex, Gemini, Pi) check for a session header or unique keys to confirm the format. Relying on #### count alone in .md files is fragile — combining the filename check from point 1 would solve this.

[mvanhorn]

Great catches. Fixed all three in 3277254:

1. Fingerprint now checks Path(filepath).name == ".aider.chat.history.md" instead of matching any .md with #### headings. CONTRIBUTING.md, CHANGELOG.md, etc. are no longer false positives.

2. Re: multi-line user messages - in Aider's actual format, the full user prompt lives on the #### line (even long ones). Lines after are always assistant output. But if we see real-world exceptions to this pattern, happy to revisit.

3. The filename check serves as the structural fingerprint (solves points 1 and 3 together).

Added test_aider_rejects_generic_md to verify regular markdown files are not parsed.

[web3guru888]

✨ Review of #172 — feat: add Aider chat history markdown normalizer

Scope: +80/−1 · 2 file(s)

• mempalace/normalize.py (modified: +40/−1)
• tests/test_normalize.py (modified: +40/−0)

Strengths

• ✅ Includes test coverage

🟢 Approved — clean, well-structured PR. Good work @mvanhorn!

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