feat(eod): allocate Pricing & Timing / Rotation basis-gap slices to specific stocks (schema 2.2)

[cipher813]

Summary

Closes alpha-engine-config-I2046. crucible-executor PR343 (schema 2.1) added per-ticker ib_market_value/market_value fields specifically as a "breadcrumb for future per-name attribution" but never used them for attribution. This PR is that follow-through: it decomposes the aggregate pricing_timing_usd sleeve (the IB-mark-vs-settled-close basis gap) per ticker instead of leaving it as a portfolio-wide generic bucket.

Why this decomposes exactly (no residual/fudge needed)

mark_basis(t) = Σ_{held today} (ib_market_value_i − market_value_i) and mark_basis(t−1) = Σ_{held yesterday} (ib_market_value_i − market_value_i), so pricing_timing_usd = mark_basis(t) − mark_basis(t−1) telescopes into an EXACT per-name sum: each ticker held on either day contributes basis_today_i − basis_prior_i (zero baseline on the day it wasn't held). This is not an approximation — the per-ticker sum equals the aggregate to the last cent, verified by new tests.

What changed

• Each held/entered name's basis-gap slice folds into its own position component's contrib_usd (exposed separately too, as position_alpha_usd [pure settled-close economic alpha] + pricing_timing_usd [this name's slice], so the breakdown isn't lost).
• Each fully-exited name's slice folds into the rotation component the same way.
• The generic "Pricing & timing" line now carries ONLY the leftover no ticker could be attributed (e.g. a legacy snapshot missing ib_market_value) — will read ~$0 on any day both snapshots have complete schema-2.1 data.
• "Unattributed" is deliberately left alone — it has no per-ticker basis in current data (fees/FX/untracked corporate actions), and force-allocating it would be a fabricated number, not a derived one (fail-loud/no-silent-allocation doctrine).
• Schema 2.1 → 2.2 (purely additive: 2 new fields on positions[], 2 new fields on alpha_attribution/nav_reconciliation).

Tests

New TestPricingTimingPerTicker class (4 cases: retained position, same-day new entry, fully-exited name, missing-data fallback) plus updated existing tests for the schema bump. Full suite: 1465 passed, 4 skipped (no regressions).

Test plan

• 1465/1465 tests green locally
• CI green
• After merge: next EOD run produces a schema-2.2 artifact; verify positions[].pricing_timing_contrib_usd populated for retained names and the "Pricing & timing" component shrinks toward $0 on a no-legacy-data day

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