Reconcile KB build status (and correct an assessment I contradicted)

[eaitbrahim]

Doc-only. No code changed.

What this fixes

Four README claims said §65.9 income-purification was NOT BUILT / deferred to go-live. It was built today in #107. Corrected in place, with the superseded reasoning kept rather than deleted. Also marks §65.4 (rail 17, #108) and §28.4's haram_sector screen (#104) as built.

⚠️ The uncomfortable part, recorded rather than smoothed

Memory carried §65.9 as "the only NEW machine-verifiable compliance obligation… highest priority". The README carried a later assessment saying the opposite, with four reasons. They contradicted each other, and I built the item from the memory framing without checking the README row first.

The outcome was defensible — two of the four deferral reasons don't hold:

• (c) "not machine-computable on this venue" assumed inferring riba from an API balance delta. It missed that the imported transaction ledger already carries typed reward rows — Reward Income, Incentives Rewards Payout, 19 in our own real history. No inference needed.
• (d) "auto-purification would violate equity.py's detect-but-never-adjust rule" doesn't apply to a report-only build that adjusts nothing — and that objection is respected, not overridden.
• (a) "P&L half already handled" was correct but incidental, and is now pinned by a test.

But all of that was found after building, not before. Had the reasons held, the work would have been wasted and a recorded decision silently reversed. The process was wrong even though the result was right.

Rules added

1. Read the README row before building a KB-derived item, not just the memory note — this file carries later assessments, because they're written when an item is checked against the code.
2. Correct overturned assessments in place, not by appending a contradicting note elsewhere. A KB that disagrees with itself is worse than one that is wrong.
3. Build status belongs in the README row. A row saying "not built" about built code misleads every future session, and this project's method depends on the KB being trustworthy.

Verification

1229 tests pass (unchanged — doc-only).

🤖 Generated with Claude Code