feat(igla): Wave Loop 891 — module-scope [601][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes

[gHashTag]

Closes #1843

Continuation of the mechanical packed-vector array-of-struct ladder.

• Adds specs/scratch/w891_bench_module_601x2p6_aos_var_call_write.t27 (38,464 elements, 1,230,848-bit packed vector, ~1.174 MiBit).
• Generator scripts/gen_w891.py copied from W890 with copy-hazard checklist cleared (OUTER=601, MID_IDX=300).
• Seal and integration test added; zero compiler / FROZEN_HASH changes.

Validation matrix:

• t27c parse / icarus-lowerable / icarus-simulate (17 cycles) / icarus-cocotb / seal --verify — all PASS.
• Targeted cargo test PASS.
• Full icarus_lowerable suite: 350 passed; 1 pre-existing corpus_classifier_matches_lean_completeness failure for specs/cloud/railway_deploy.t27.

🤖 Generated with Claude Code

[gHashTag]

Closing — nothing left to land once this is measured against current master

Checked with the GitHub API against master at 10e3d5e71a970351d5d1c63f0dd88b77210dbffc. Every durable file in this PR is already on master, byte-identical (same git blob SHA):

• .claude/plans/wave-loop-*.md, docs/reports/FPGA_LOOP_CLOSEOUT_W*.md, scripts/gen_w*.py — all SAME-BLOB with master. The accumulated W890–W898 record landed via feat(igla): Wave Loop 898 — module-scope [615][2]^6 Pt non-power-of-two outer-dimension array-of-struct variable from call with indexed signed writes #1900, merge commit e756e8c3300e96b35682f8394b405f529683e78c.
• .trinity/experience.md and .claude/skills/t27-wave-loop.md additions — already present on master verbatim.
• bootstrap/tests/icarus_lowerable.rs — master's copy already carries all 352 accepts_w* tests, including accepts_w891_bench_module_*_aos_var_call_write. The large +1872-style line count here is an artifact of an ~848-commit-old merge base, not new content. No test is removed by this close, and the branch is left in place.

What is genuinely unique to this PR is not landable:

Path	Why not
specs/scratch/w*_bench_module_*.t27	specs/scratch/ is gitignored (.gitignore:113) and does not exist on master at all
.trinity/seals/scratch_*.json	gitignored (.gitignore:120); master carries zero scratch_* seals, so re-adding one would red the seal gate
docs/NOW.md	frozen archive since #2298 — new entries go to docs/now/<date>-<slug>.md. This PR prepends to the frozen file, and that prose is in Russian, against the English-only rule
.trinity/current-issue.md, .claude/skills/t27-master-executor.md, .claude/skills/wave-loop-autopilot.md	live status pointers, superseded by wave 898/899

Wave 891's work is on master; only gitignored scratch material remains here, so this closes rather than being rebased.

Series close-out: #1810, #1813, #1842, #1844, #1847, #1850, #1852, #1854, #1856 and #1858 are all closed for this reason. #1815 was the only PR in the series with unique durable content — the Wave Loop 883 experience entry and skill example, the .claude/plans/wave-loop-884.md plan, and the W883 close-out and W884 cooperation reports, none of which exist on master. It was rebuilt on top of master (scratch spec and scratch seals dropped) and left open with auto-merge armed.