Nested Schema Validation & Type mismatch check

[AbhinRustagi]

What this PR does

Previously the parser only checked that required top-level props were present — nested data was never validated, and a wrong-typed value flowed straight to the renderer. This PR adds recursive JSON-Schema validation of all component props (objects, arrays, scalar/enum leaves, and component elements in data positions), and applies one consistent resolution rule to every invalid value instead of either ignoring it or blanking the UI:

invalid value at an edge:
  1. schema has a `default`  →  substitute it (error still reported)
  2. edge is REQUIRED        →  parent becomes invalid; same rule one level up
  3. edge is OPTIONAL        →  prune the value
array items: always pruned  →  one bad row never takes down the table

At the outermost edge (component param), "propagate" means drop the component. Net effect: a deep violation can only blank the root if every edge on the path is required and none is an array item — i.e. only when the tree genuinely cannot satisfy the schema. LLM output degrades gracefully; the error always reaches the host's onError for the correction loop.

Cases covered

#	Case	Handling
Top-level args
1	Required arg, type/enum mismatch, default provided	Substitute default, keep error
2	Required arg, type/enum mismatch, no default	Drop component
3	Optional arg, mismatch, default provided	Substitute default, keep error
4	Optional arg, mismatch, no default	Drop the arg (prop pruned)
5	Required arg absent/null, default provided	Fill silently, no error (pre-existing)
6	Required arg absent/null, no default	Error + drop component (pre-existing)
7	Excess positional args	Reported, extras dropped (pre-existing)
Nested objects
8	Required child key invalid, child has default	Substitute child default; parent survives
9	Required child key invalid, no default	Parent invalid → rule repeats one level up
10	Optional child key invalid, default provided	Substitute default
11	Optional child key invalid, no default	Prune the key; parent survives
12	Required child key absent/null, default provided	Fill silently, no error
13	Required child key absent/null, no default	Error (missing-required/null-required) + parent invalid
14	Wrong container kind (scalar/array where object expected, etc.)	type-mismatch → resolution rule
Arrays
15	Any invalid item (bad type, missing required key, misplaced component)	Item pruned, siblings kept — arrays never invalidate; error paths keep original indices
16	Non-array where array expected	type-mismatch → resolution rule
Components in data positions
17	Element where a plain-data shape is declared (e.g. HorizontalBarChart(Card([]), …))	type-mismatch ("expects array but got component Card") → resolution rule
18	Element in a component slot ($ref/anyOf)	Skipped — slot membership deferred (see below)
19	Misplaced component's own args	Still validated independently; both errors surface
Streaming
20	Required-key checks mid-stream	Deferred while partial; fire on completion
21	Enum membership mid-stream (e.g. Badge("prim cut mid-token)	Deferred — a partial literal may still complete to a valid member; judged at completion
22	Scalar type checks mid-stream	Active — a wrong scalar type can't become right by streaming more
Conservative skips (unchecked by design)
23	Composite schemas ($ref/anyOf/oneOf/allOf) for plain values	Skipped
24	Dynamic values ($var, builtins)	Skipped — resolve at runtime
25	Malformed schema fragments (unknown type, tuple items, non-array required)	Skipped
26	Schema default values themselves	Trusted, not validated

Deferred (explicit non-goals here)

• $ref resolution — data behind $ref (e.g. chart Series) is still unchecked; biggest coverage gap, planned next.
• Slot membership — "is this component allowed in this children slot" (helper existed, backed out to keep scope).
• Per-statement streaming partial (checks currently gate on whole-document completeness); additionalProperties; constraint keywords (minItems, pattern, …).