fix: preserve direct short reversal affordability

[luisleo526]

Summary

• Extend the generic omitted-quantity, 100%-of-equity market-short
  affordability lifecycle to direct LONG-to-SHORT auto-reversals at 100%
  short margin.
• Preserve that lifecycle across broker margin reductions, while clearing it
  on script-driven reductions, accepted adds, fresh/raw openings, full closes,
  and run reset.
• Keep the configured full-residual liquidation interpretation ahead of the
  one-contract floor-zero fallback.
• Add positive and exclusion coverage for explicit quantity, non-100% sizing,
  other margins, priced orders, slippage, process-on-close, calc-on-fill,
  magnifier, streaming, OCA membership, lifecycle mutations, and reset
  behavior.

Generic-semantics guard

Strategy-specific fixes are forbidden. The changed production code contains
no slug, author, title, filename, source-text pattern, corpus metadata,
strategy-name, indicator-name, or specific order-ID predicates. Eligibility is
derived only from broker-visible order topology, sizing, margin, execution
phase, and position lifecycle state. Validation strategies are witnesses, not
production selectors.

Validation

• Clean-room Pine v6 TradingView oracle: 3/3 variants agree.
• Exhaustive N=3 masking matrix: all 8 2^3 cells completed; B-only was the
  sole active zero-DOWN cell.
• Focused C++ test: 86/86 assertions.
• Full CTest with Python 3.13.13 pinned: 121/121.
• Fixed nine-witness production route: 9/9 status OK; tapes and receipts are
  byte-identical to the accepted exploratory cell; ordinary ABI, zero matrix
  macros, and zero automatic ladder invocations.
• Public corpus driver: 252/252 OK, 2 tier UP, 0 tier DOWN.
• Full publication sweep: 416/416 classified; 409 OK, one established
  no-trades row, five established transpile errors, one established run error,
  and zero compile/driver/timeout errors.
• Full tier board: 364 Excellent / 38 Strong / 3 Moderate / 2 Weak to
  365 Excellent / 37 Strong / 3 Moderate / 2 Weak; 1 tier UP, 0 tier DOWN.
• Full-sweep source, TradingView tape, metrics, metadata, and input manifests
  were byte-identical before and after.

The full sweep changed 15 engine trade tapes. This PR therefore claims
0 tier DOWN, not the broader claim that every underlying metric is
monotonic. The sole tier promotion was
markittick-alpha-signal-engine-pro-markittick, Strong to Excellent
(exitP90 0.0239 -> 0.0016, pnlP90 1.1697 -> 0.0842).

Immutable pins

• Base engine: a12cdbc43b284a440a1dc3ad8f33a3cdb5f1f643
• Candidate engine: b66971dd18dc09d5552e6631483be29948d653c1
• Candidate tree: ab690a62cb18b05f3bbf3d16c2ec06be07555380
• Codegen: bc97151503ae2cafccbe298b188488bf84f24439
• Scraper: 075b271bb0bfcd0908daccf8f1d79a7ab0991602

Two preserved preflight attempts failed before semantic execution because of
system Python 3.8 and a missing generated version header. The successful gates
above pinned Python 3.13.13 and a standard candidate build.

[Copilot]

Pull request overview

This PR extends the engine’s “omitted-quantity, 100% of equity, MARKET short at 100% short margin” affordability + lifecycle semantics so they also apply to direct LONG→SHORT auto-reversals, and ensures that provenance is preserved across broker-driven margin reductions while being cleared on script-driven lifecycle mutations and resets.

Changes:

• Add a new lifecycle provenance bit for direct LONG→SHORT default-sized MARKET reversals, and thread it through fill classification and margin-call fallback selection.
• Clear the new provenance on position resets, fresh openings, adds, and script-driven reductions; preserve it across broker margin-call reductions.
• Add a focused, high-coverage test suite and wire it into the CTest build.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
tests/test_direct_short_reversal_affordability.cpp	New focused test harness covering direct short-reversal affordability lifecycle behavior, exclusions, and reset/mutation rules.
tests/CMakeLists.txt	Registers the new test target in the test suite build.
src/engine_orders.cpp	Ensures the new direct-reversal lifecycle provenance is cleared on full resets, fresh openings, and script-driven partial reductions (but not broker margin-call reductions).
src/engine_fills.cpp	Detects eligible direct LONG→SHORT default-sized reversals at fill time, sets/clears the new provenance, and includes it in floor-zero / one-contract fallback selection during margin calls.
include/pineforge/engine.hpp	Documents and adds the new per-position lifecycle provenance flag for direct short reversals; updates existing short-opening event docs.

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