feat: CLI v0.2.0 — memweave index/add/files/search/stats

[sachinsharma9780]

Full details on command design, flag mapping, and acceptance criteria are in the issue. This PR is the implementation.

What's in this PR

New: memweave/cli.py — five Click commands, each a thin wrapper over an existing MemWeave public method. No new core logic.

Command	Wraps
memweave index	mem.index()
memweave add <file>	mem.add()
memweave files	mem.files()
memweave search <query>	mem.search()
memweave stats	mem.status()

All commands support --workspace / -w, --embedding-model, and --json. Search exposes the full API surface: --strategy, --min-score, --max-results, --source-filter, --mmr-lambda, --decay-half-life-days, --snippet-chars.

Bug fixes in store.py (discovered during development):

• _startup_dirty_check() — stats was always reporting dirty=True because _dirty is in-memory and never persisted. Added a startup scan that compares the files table against disk and sets _dirty=False when the index is current.
• MMR lambda kwarg ignored — MMRReranker was always constructed with cfg.mmr.lambda_param even when mmr_lambda was passed per-call. The computed value was silently dropped.
• Temporal decay half-life kwarg ignored — same pattern: TemporalDecayProcessor ignored decay_half_life_days and always used the config default.

Tests

• tests/unit/cli/ — 6 files, all commands covered with Click's test runner and AsyncMock. No API key needed.
• tests/integration/test_cli_*.py — 5 files, end-to-end against a real index.
• tests/unit/test_store.py — TestStartupDirtyCheck (5 tests) and TestApplyPostprocessors (8 tests) added to prevent the above bugs from regressing undetected in CI.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 98.43750% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.74%. Comparing base (d8d3988) to head (6720df0).

Files with missing lines	Patch %	Lines
memweave/store.py	88.88%	2 Missing ⚠️
memweave/cli.py	99.42%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main       #5      +/-   ##
==========================================
+ Coverage   88.27%   89.74%   +1.47%     
==========================================
  Files          25       26       +1     
  Lines        1672     1863     +191     
==========================================
+ Hits         1476     1672     +196     
+ Misses        196      191       -5     

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