spec(port): port specs/port/trios-railway/crates/trios-igla-race/src/ema.t27 (Closes #9683)

[dmitrii-f-t27]

Summary

Port gHashTag/trios-railway:crates/trios-igla-race/src/ema.rs (at 385c2143ef46, 18 lines) as specs/port/trios-railway/crates/trios-igla-race/src/ema.t27 — Roadmap Stage 6 (goal #4548), target t27c gen-rust. Closes #9683.

The original tracks an exponential moving average: new builds the tracker with its alpha and no value; update seeds the average with the first sample, then blends every following sample as v * (1 - alpha) + x * alpha.

Per the issue's rule ("Port the decision, not the plumbing"), both listed functions are ported under their names as pure functions — the Rust Option<f64> value becomes the presence flag on the port's state, and the &mut self threading becomes the state chain — with 6 tests (11 runtime asserts, 0 vacuous, 100% function coverage):

• EmaTracker_new — the unseeded start (original lines 6-9);
• EmaTracker_update — the two decisions: an unseeded tracker takes the sample as its value (the seed, original line 14), a seeded one blends it (original line 13);
• ema_blend — the blend formula, tested directly and at the alpha extremes: alpha 0 freezes the average, alpha 1 tracks the sample.

Verification (all run live from the worktree root, zig 0.16.0)

• t27c parse: OK. t27c spec-status: IMPLEMENTED. t27c typecheck: 0 errors, 0 warnings.
• t27c coverage: 3/3 tested (100%) — no transports in this port.
• t27c test-report: 6 tests / 6 pass / 0 FAIL / 0 BLOCKED, 0 vacuous passes.
• t27c gen | grep -c 'not yet implemented': 0; gen | wc -l: 65 (> 12).
• grep -cE '^\s*(pub )?fn (EmaTracker_new|EmaTracker_update)\(': 2. grep -cE '^\s*test\s+(["|[A-Za-z_])': 6 (≥ 2).
• Boundary: git status --short — exactly this one file. The repo's lefthook pre-commit passed.
• dupe_scan: all 3 names unique across 2040 specs; the bare body scan adds no duplicate group (752 bodies / 221 groups on base, identical with this spec present).

Dmitrii Fedorov (@dmitrii-f-t27)

[dmitrii-f-t27]

@gHashTag Please merge this PR into master via the golden chain — rights on gHashTag/t27 are read-only for me (403), so the merge itself needs your action.

What this is: the #9683 port — crates/trios-igla-race/src/ema.rs (gHashTag/trios-railway, at 385c2143ef46, 18 lines) re-authored as specs/port/trios-railway/crates/trios-igla-race/src/ema.t27. One file, head df1ed2d6e, Closes #9683.

What is verified:

• t27c parse OK, spec-status IMPLEMENTED, typecheck 0 errors / 0 warnings, coverage 3/3 (100%) — no transports, t27c test-report 6 tests / 6 pass / 0 FAIL / 0 BLOCKED, 0 vacuous — the unseeded start, the first-sample seed, the blend formula directly, the blend after the seed, and both alpha extremes (0 freezes, 1 tracks).
• gen → 65 lines, 0 not yet implemented; the 2 required names count exactly 2; 6 test blocks; boundary exactly the one file.
• dupe_scan: all 3 names unique across 2040 specs; bare body scan adds no duplicate group (752/221 unchanged).
• The t27b-native-run artifact of this head (commit df1ed2d, run 38999903674): ema.t27 row — reference pass, t27b pass, tests 6, invariants 0, asserts 11, blockers [], detail empty, reference_disagree: [].

CI (head df1ed2d): required trio green — validate, check-linked-issue, parse-ratchet; 26 checks pass overall, incl. emit-bitexact, t27b-native-linux, t27b-native-macos.

The 3 reds are the base-red trio, not this change: cli-tri (the #3324 include_str!), duplicate-bodies (only the known base names), t27b-native-ratchet (the same verdict red the Queen's port PRs carry; this spec's own row is reference pass + t27b pass — the registration debt is the UNLISTED class).

After the merge I will: verify the spec file live on the merge SHA, confirm #9683 auto-closed, and file the 14-step report.

Dmitrii Fedorov (@dmitrii-f-t27)