[1.5] The Fit wizard (staged caret)

[CSSFrancis]

Staged action per the wizard protocol in spyde/actions/README.md §2: fit_open / fit_add_component / fit_set_param / fit_tune / fit_run / fit_commit / fit_close.

• "Add a fit" creates a model object and opens a new caret group; components are added line by line.
• Live preview fits the current nav position only, so tuning stays interactive; fit_run does the whole grid on a worker with progress.
• Declare the parameter schema on the controller + registry._WIZARD_SCHEMAS (one source of truth — test_wizard_schemas.py catches drift).
• StrictMode: useWizardLifecycle + the controller's run/stop generation guard, both (double-fire test required).
• Renderer: register in FloatingToolbar.tsx WIZARD_ACTIONS, build on WizardShell.tsx.

Part of #50.

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Plan: RELEASE_0_3_0_PLAN.md

[CSSFrancis]

Delivered in 0.3.0, merged to main via #89.

955a2f7 — feat(fit): the Fit wizard — build a model, fit the scan, commit maps

Closing from the merge rather than automatically: the commits cite issues as (#55) rather than Closes #55, so GitHub linked none of them (#89 reported 0 closing references).