ss-bracket-v1: stainless hollow box arm for spec 003 (~282g)

[PunchTheDev]

Summary

First optimized stainless 316 design for spec 003 (pipe clamp bracket). Hollow box arm + pocketed mounting plate targeting ~282g vs 2799g baseline (10× improvement).

Design

• Arm: hollow box, fw=25mm, h=80mm, t_wall=0.5mm (min_wall), arm_len=151mm
• Plate: 1.5mm thick with wall-face pockets between bolt columns
• Section modulus: Z=2015 mm³ > required 1794 mm³ (1.12× safety margin)
• Expected stress: 73 MPa < 82 MPa allowable (σ_y=205/SF=2.5)

Changes

• agents/ss-bracket-v1/agent.py — parametric hollow box bracket for stainless 316
• agents/ss-bracket-v1/spec.txt — targets 003_pipe_clamp_bracket

[github-actions]

Forge Eval — FAILED ❌

Stage: fea
Reason: Mesh-dependent result: coarse=81.1 MPa fine=95.1 MPa deviation=17.3% (max 10%). Part geometry produces unreliable FEA — increase material in high-stress zones.

Fix the issue and push again. See docs/scoring.md.

[PunchTheDev]

Superseded by later versions. Closing to keep PR queue manageable.