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

[RichardHightower]

Closing in favor of #27, which carries the same feature plus the review feedback applied:

• Pure pick_summarizer_kind(settings, key_available) -> SummarizerKind decision function so tests assert on the branch taken (was: only verified non-panic with let _ = summarizer;).
• resolve_api_key simplified from (Option<String>, &'static str) to Option<String> (the second element was always discarded by the only caller).
• pub → pub(crate) on build_summarizer, env_var_for_provider, pick_summarizer_kind (memory-daemon is lib+bin, so pub was leaking test helpers).
• is_anthropic / is_openai / default_env_var_for_provider helpers using eq_ignore_ascii_case (was: 3 sites of .to_lowercase()).
• warn! on unknown providers before fail-open to OpenAI (was: silent).
• Tests: 7 → 16, including the precedence regression guard the PR description claimed but didn't actually have.

The ROADMAP/STATE edits from this PR are reverted in #27 because they collide with the unpushed local v3.0 plan (Phase 51 = Retrieval Orchestrator, not Summarizer Wiring). The summarizer wiring will get its own slot in v3.0 via a follow-up (likely Phase 54).