fix build/distribution spec: npm deps not workspace, align configs with sibling projects, resolve review issues

- Replace workspace:* deps with published npm semver ranges (^0.34.49, ^0.1.0)
- Expand package.json: add description, publishConfig, scripts, engines,
  devDependencies, conditional exports with types/default for import+require
- Fix tsup entry names (path-prefixed like ujsx), add target: es2022,
  remove splitting:true (not used by sibling projects)
- Align tsconfig with sibling projects: add lib, noUncheckedIndexedAccess,
  noUnusedLocals, noUnusedParameters, erasableSyntaxOnly, etc.
- Expand vitest.config.ts with include, coverage, and path alias
- Clarify @preact/signals-core as direct dep (not just transitive via ujsx)
- Clarify @alkdev/pubsub is a consumer dependency, not flowgraph's dep
- Fix edge key convention: document composite key format for call graph's
  multi-edge-type scenario (triggered + depends_on between same pair)
- Align OperationEdgeAttrs field naming: use detail+mismatches consistently
  instead of compatibilityDetail
- Add InvalidInputError to error hierarchy (referenced in flowgraph-api but
  was missing)
- Fix undefined attrs.category reference in reactive-execution.md
- Remove internal drafting note from host-configs.md
- Fix ReactiveHostConfig constructor signature inconsistency across docs
- Constrain TemplateEdgeAttrs.edgeType to sequential|conditional only

docs/architecture/error-handling.md

@@ -25,7 +25,8 @@ FlowgraphError                    # Base class for all flowgraph errors
 │   ├── DuplicateNodeError         # Duplicate node key
 │   ├── DuplicateEdgeError         # Duplicate edge key
 │   ├── NodeNotFoundError          # Referenced node doesn't exist
-│   └── CycleError                 # Adding an edge would create a cycle
+│   ├── CycleError                 # Adding an edge would create a cycle
+│   └── InvalidInputError          # Invalid input to fromJSON() or constructor
 ├── ValidationError                # Schema validation failed (single field)
 ├── GraphValidationError           # Graph-level validation issue
 │   ├── CycleValidationError       # Cycle detected in the graph
@@ -117,6 +118,19 @@ Thrown when adding an edge would create a cycle. The `cycles` field contains the
 
 Note: `CycleError` is flowgraph's cycle error, thrown by `addEdge()` during construction. Taskgraph uses a different error name (`CircularDependencyError`, thrown by `topologicalOrder()`). The two are distinct errors for distinct contexts — flowgraph prevents cycles at construction time, taskgraph allows cycles and detects them later.
 
+### InvalidInputError
+
+```typescript
+class InvalidInputError extends ConstructionError {
+  constructor(public readonly errors: ValidationError[]) {
+    super(`Invalid input: ${errors.length} validation error(s)`);
+    this.name = "InvalidInputError";
+  }
+}
+```
+
+Thrown by `fromJSON()` when the input data fails schema validation. The `errors` field contains the array of `ValidationError` objects describing which fields failed validation. This is distinct from `ValidationError` (which is a returned result) — `InvalidInputError` is thrown because `fromJSON()` enforces that deserialized data is structurally valid.
+
 ### ValidationError
 
 ```typescript
@@ -231,6 +245,7 @@ The distinction between thrown errors and returned errors:
 | `addNode(key, attrs)` | Throws `DuplicateNodeError` on duplicate key | Adding a duplicate is a programmer error |
 | `addEdge(source, target)` | Throws `NodeNotFoundError` on missing endpoint | Edge without endpoints is invalid |
 | `addEdge(source, target)` | Throws `CycleError` if edge creates cycle | DAG invariant must be maintained |
+| `fromJSON(data)` | Throws `InvalidInputError` on validation failure | Deserialized data must be structurally valid |
 | `updateNodeStatus(id, status)` | Throws `InvalidTransitionError` on invalid transition | State machine must be enforced |
 | `validateSchema()` | Returns `ValidationError[]` | Schema issues are validations, not crashes |
 | `validateGraph()` | Returns `GraphValidationError[]` | Graph issues are validations, not crashes |