v0.5.0 — the structural-advantage release

Six capabilities the incumbents structurally cannot ship — binary files,
ordinal identity, and GUI-first architectures forbid every one of them.

The type system for hardware (ADR-0015)

Pins carry electrical envelopes; net voltages derive from rail names
(+3V3 -> 3.3 — a name that parses is a contract). 5V into a 3.6V-max pin
is a design-time type error. Rail overload checked against source
capacity, utilization reported even when green, coverage counted so
green never masquerades as verified. schematic_envelope.

Pull requests that show their physics

gitcad-review --base main: per changed design doc — semantic diff,
check delta (violations INTRODUCED vs FIXED vs PRE-EXISTING across ERC /
envelopes / board validation / DRC), before/after renders side-by-side.
The merge gate fails only on introduced violations. Exit 1 = CI gate.

Simulation as tests

to_spice exports the schematic (rails become sources by the same name
contract; unmodeled parts REPORTED, never dropped). sim_check runs
ngspice asserting node voltages — "OUT sits at 2.5 +/- 0.05 V" is now a
check like any other.

Semantic 3-way merge (ADR-0016)

gitcad-merge is a git merge driver keyed by stable identity: features
by id, schematic connectivity by pin. Parallel edits to different
features merge into a document that rebuilds; a net rename merges; the
same pin on two nets conflicts — structured conflicts, never text
markers. The file-lock era ends here.

Requirements as code

gitcad-verify requirements.json: named requirements bound to machine
checks (mass, volume, bbox, ERC, envelopes, rail utilization, DRC) —
the traceability matrix that executes, measured-vs-limit per row.
Unchecked requirements are visible debt, never silent green.

Fab-lot traceability

gitcad-lot record: a physical build pinned to the exact commit and the
sha256 of every artifact sent to the fab; tampering names the file.
Field failure on lot 7? git bisect run gitcad-verify requirements.json.

Plus: the design-review GUI

Tabs 3d | schematics | measure; click-to-select with part info; exploded
-view slider (display-only, #x=0.6 deep links); the electrical sheets
that make up an assembly rendered under its 3D model; point-to-point
measure with vertex snap.

294 tests. Every commit CI-verified green.