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 #1843

Next mechanical step in the packed-vector array-of-struct ladder.

• Outer dimension: 601 (non-power-of-two)
• Inner struct: [2]^6 Pt (384 bits per element)
• Total elements: 601 × 64 = 38,464
• Packed vector width: 38,464 × 32 = 1,230,848 bits (~1.174 MiBit)

Pattern: module-scope variable initialized from a pure function call, mutated via signed-index field writes, read back with assert_eq inside a bench block.

Expected zero compiler / FROZEN_HASH changes.

🤖 Generated with Claude Code

User Scenarios

• Given a module-scope variable of a packed-vector array-of-struct with outer dimension 601 (non-power-of-two) and inner struct [2]^6 Pt, When the variable is initialized from a pure function call and then mutated via signed-index field writes, Then reading back with assert_eq inside a bench block must produce the expected values with zero compiler or FROZEN_HASH changes.

Requirements

• FR-001: The spec MUST declare a module-scope variable with outer dimension 601 and inner struct [2]^6 Pt (384 bits per element, 38,464 total elements).
• FR-002: The variable MUST be initialized from a pure function call.
• FR-003: The test MUST mutate the variable via signed-index field writes.
• FR-004: The test MUST read back values with assert_eq inside a bench block.
• FR-005: The change MUST NOT modify compiler behavior or FROZEN_HASH seals.

Success Criteria

• t27c specs/tools/tri/loop.t27 exits 0
• 1 new bench test passes in specs/tools/tri/loop.t27 for Wave Loop 891 pattern
• .trinity/seals/Power.json remains unchanged (exit 0 on seal verification)

Boundary

• specs/tools/tri/loop.t27