feat(ir): stamp ir_version into every IR projection; emitters validate before rendering (#62)

[danielPoloWork]

Problem (#62)

Manifests carry schema_version: 1, but the emitted IR JSON carried no version or schema marker. The IR is a persisted artifact (build/*.json) that outlives tool runs and crosses the determinism boundary into five emitters — yet an emitter couldn't tell whether the JSON it received matched the contract it was written for. When a block type or field is renamed, an old cached IR (or an IR from a newer render) mis-renders silently: unknown block types already fall through to return "" in _flatten/_line.

Fix

• render.py — IR_VERSION = 1 + GENERATOR = "eamos-render", stamped as the first two fields of all six projections (deck, infographic, data, mindmap, quiz, topology). Bump policy: ir_version increments on any breaking change to block/field shapes.

• New _cli.require_ir_version(ir, tool, supported) — every emitter (emit_md, emit_pptx, emit_docx, emit_svg, emit_xlsx) validates right after loading the artifact, each pinning its own SUPPORTED_IR_VERSION = 1. A mismatch — or an absent field, i.e. a pre-feat(ir): stamp ir_version into every IR projection; emitters validate before rendering #62 artifact — is refused with one actionable line:

  emit_md: IR version None not supported (expected 1); re-render the manifest
  

• os/deck-ir/_schema.md documents both fields and adds the Versioned contract invariant.

Tests

• All six projections stamp ir_version == render.IR_VERSION and generator.
• Reject path: emit_md on an unversioned IR exits non-zero in a subprocess with the message above, no traceback. Accept path: a fresh render → emit_md round-trips clean.
• Determinism smoke unaffected (two renders byte-identical); 90/90 tests green.

Closes #62

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