estimate.ts: size scriptless problem_spec solves from typed spec fields (drop the Julia-source regexes)

[aarontrowbridge]

Roadmap context: vault plan `plan-20260812-142100-problemspecs-issimo-roadmap` (W2.3).

The problem

`packages/amico-run/src/estimate.ts` scrapes `N`/`levels` out of Julia source with regexes (`extractKeyVars`) — and rejects scriptless `problem_spec` solvespecs outright ("no script to size"). Once Phase 3 (#340) makes spec-authored solves the default path, the estimator must not be the step that still demands a script.

Tasks

• When the solvespec carries `problem_spec`, parse it (smol-toml) and read the typed fields: `problem.N`, `system.params.levels` (per-component for composites), `pulse.T`, trajectory kind (unitary vs ket vs density drives the dimension scaling), wrapper count (sampling multiplies).
• Emit the same `{sizeClass, estimatedBytes, localRamBytes, offloadSuggested, reason}` JSON contract — the estimator's output shape is unchanged; only the input adapter is new.
• Keep the regex path for script solves (free tier isn't going away); share the size model between both adapters.
• Fixtures: minimal/rich/wrapped problemspec TOMLs from `packages/schema/test/fixtures` reused as estimator inputs.

Acceptance

• `amico-run estimate` on a scriptless `problem_spec` solvespec prints the standard estimate JSON; numbers match the script-path estimate for an equivalent authored script within the model's own tolerance.