feat(v3.0): wire API-based summarizer from config

[RichardHightower]

Summary

Wires the existing ApiSummarizer (OpenAI + Anthropic) into the daemon from config and environment variables. Previously hardcoded to MockSummarizer with a TODO comment.

What changed

File	Change
crates/memory-daemon/src/commands.rs	build_summarizer() function: reads provider/model from config, resolves API key from env var or config, constructs ApiSummarizer or falls back to MockSummarizer with warning. 7 unit tests.
crates/memory-types/src/config.rs	Added api_key_env: Option<String> to SummarizerSettings for custom env var override (serde(default) for backward compat)
.planning/STATE.md, .planning/ROADMAP.md	v3.0 progress updated

How it works

# ~/.config/agent-memory/config.toml
[summarizer]
provider = "openai"          # or "anthropic"
model = "gpt-4o-mini"        # or "claude-3-haiku-20240307"
# api_key_env = "MY_KEY"     # optional override, defaults to OPENAI_API_KEY / ANTHROPIC_API_KEY

Set the corresponding env var (OPENAI_API_KEY or ANTHROPIC_API_KEY) and the daemon picks it up automatically. Without an API key, it falls back to MockSummarizer with a warning log.

Design decisions

• Env-var-first for secrets — API keys stay out of config files. Config can optionally override which env var to read via api_key_env.
• Backward compatible — new field is Option<String> with serde(default), existing configs unchanged.
• Fail-open — missing API key logs a warning and falls back to mock, never blocks startup.
• Case-insensitive provider matching — OpenAI, openai, OPENAI all work.

Tests

7 unit tests covering:

• Provider → env var mapping (openai, anthropic, custom)
• Case-insensitive provider matching
• Explicit key in config takes precedence over env var
• Env var lookup for both providers
• Fallback to mock when no key available