feat(compliance): the asymmetric lower-bound liquidity gate (#696, pa…

[eaitbrahim]

…rt 2 of 2)

Part 1 recorded WHICH feed a series came from. This is what reads it.

THE GATE. Venue volume is a LOWER BOUND on consolidated volume, never an upper one, so the two directions are not equally informative and the gate treats them differently:

• at or above the floor, on ANY feed -> CONCLUSIVE PASS. A name that traded that much on one venue alone necessarily traded at least that much in total. A gate that refused here would ban MSFT and AAPL for thinness they do not have, and would turn a data-vendor pricing tier into a prerequisite for running the engine at all.
• below the floor, on a partial feed -> NOT A VERDICT. Equally consistent with a thin asset and with a liquid one that barely trades HERE. Refused as liquidity_unmeasured, naming the feed and both dollar figures, and saying consolidated volume is UNMEASURED rather than low. A test asserts the line never contains "illiquid" or "too thin": the refusal must not assert the half it cannot see.
• below the floor, on a consolidated feed -> unchanged. The crypto path is untouched, because Coinbase's own volume IS the scale the floor was calibrated against.
• below the floor, scope UNRECORDED -> unchanged verdict, annotated. Every series cached before v17 is unrecorded, and treating unrecorded as partial would refuse the entire existing universe over metadata nobody wrote down. It self-heals as series are re-fetched.

market_facts reads ONE_DAY provenance specifically -- that is the granularity the statistic medians, so an hourly series on another feed says nothing about it.

doctor gains data.feed_scope, WARN and never FAIL: a free single-venue tier is a legitimate configuration, and the bound admits its liquid names honestly. What is not legitimate is not knowing, and the screen only speaks for a candidate somebody is actively screening while slippage_for_quote_volume prices off the same number every cycle in silence. Partial and unrecorded series are reported SEPARATELY: one should be re-fetched under a different feed, the other may already be consolidated.

The cost-fidelity record is amended rather than rewritten (docs/experiments is append-only). The amendment retracts two claims that were asserted rather than measured -- "roughly 2% ... approximately IEX's share" (IEX publishes ~3.8% for Q2 2026, so the figure was simply wrong) and the "~50x" understatement -- notes that no number in the document depended on either, and records that what shipped is better than what that section proposed.

Tests (written first, red before green): 27 across three files.
tests/compliance/test_liquidity_lower_bound.py -- 11
tests/compliance/test_market_facts_carries_feed_scope.py -- 6
tests/commands/test_doctor_feed_scope.py -- 8 (+2 existing)

Two EXISTING reachability guards -- one in tests/compliance, one in tests/test_proposer -- correctly failed: they assert every DATA_DERIVED_FAILURES tag really appears in screen_asset output, and liquidity / liquidity_unmeasured are mutually exclusive by construction, so no single set of facts emits both. Both now screen the partial-feed arm too, rather than the tag being dropped as unreachable.

Mutation-verified, 7 mutants. One SURVIVED first time: gutting the fix line's explanatory half left keel fetch intact, and the assertion only looked for "keel". Re-fetching under the SAME feed changes nothing, so the pin now requires the word "consolidated" -- an operator who re-fetches identically gets the same warning and concludes the report is broken.

Closes #696

Claude-Session: https://claude.ai/code/session_01NzuKAe2RVrPt9acVAWjRyL

What & why

Tests-first evidence

• Tests written first, seen failing for the right reason

Gates (all must pass)

• uv run ruff check clean
• uv run mypy clean
• uv run pytest -q green

Scope check

• This PR touches a rail or a default classification — checked means it DOES;
  leave checked only if true, and if so: cite the source and open the discussion
  BEFORE review (CONTRIBUTING.md, "Governance: rulings vs. machinery").
• New dependency added (needs discussion first)