Add Aetheris V2.0 Phase 1 scope contract

[yuechen-li-dev]

Motivation

• Provide a concise, authoritative scope contract for Aetheris V2.0 Phase 1 that captures the product soft-pivot toward a sellable manufacturing-intent workflow over existing STEP/AP242 models.
• Clarify what Phase 1 is and is not so future implementation work remains strictly bounded (focus: PMI/tolerances/DFM and validation; exclude full CAD modeling).
• Establish language and product doctrine (Firmament/Forge/PMI) to ensure auditable, data-first manufacturing intent and to guide subsequent Codex milestones.

Description

• Added docs/v2/aetheris-v2-phase1-scope-contract.md containing the executive summary, product wedge, explicit non-goals, Firmament language doctrine, let/typed-values guidance, tolerance and arithmetic doctrines, Forge concept-family direction, pmi doctrine, minimal Phase 1 feature set, validation philosophy, an example Firmament file, and a recommended implementation order.
• Key scope decision: Phase 1 is a STEP/AP242 manufacturing-intent workbench operating on existing models (canonicalize/import → analyze/map/label → author PMI/tolerances → Forge DFM checks → export enriched AP242 + validation report), not a full CAD modeling/compiler milestone.
• Major non-goals recorded: full CAD modeling from scratch, arbitrary decompilation, feature-history recovery, generic fillet/chamfer/loft modeling, AI-driven CAD UI modeling, graphical PMI/layout, full drawing replacement, Turing-complete scripting, hidden state machines, and similar broad efforts.
• Language doctrine summary and constraints: Firmament V2.0 is pure typed manufacturing-intent data using immutable let bindings, acyclic expression graphs, no conditionals/loops/functions/mutation, unit-aware typed values, required tolerances for PMI-emitted dimensions, basic arithmetic only, and pmi record-shaped authoring; Forge moves to extensible concept-family descriptors rather than parser hardcoding.
• Planned implementation order included in the document: L1 let literals, L2 record groups/dotted refs, L3 arithmetic/acyclic validation, L4 tolerance syntax, F1 Forge concept-family syntax, P1 PMI v2 records, R1 validation/report integration, D1 demo packet.
• Documentation-only change: no parser, compiler, exporter, or runtime behavior was modified.

Testing

• Ran dotnet restore Aetheris.slnx and it completed successfully.
• Ran dotnet build Aetheris.slnx -f net10.0 --no-restore /m:1 and the build succeeded (existing compiler/analyzer warnings were reported but no errors).
• Ran dotnet run --project Aetheris.CLI -- --help to validate the CLI is functional and it produced the expected usage output.
• Performed repository validation: git diff --check passed and git status --short showed only the intended docs changes during the workflow (clean state after committing the new document).

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Codex Task