Add typed history states

[SandroMaglione]

Summary

• add shallow and deep history pseudo-states to schema-first machine definitions
• add zero-argument, path-safe target.history builders and typed defaults for first use
• preserve validated state values for deep restoration and require fresh typed initializers only where shallow restoration descends
• persist and validate history records across snapshot encoding and decoding
• document history semantics and add a minor changeset

Semantics

History nodes are routing pseudo-states: they have no schema, never become active, and are excluded from ordinary state identifiers, snapshots, initial builders, and local/branch/full targets.

Each history node owns one overwriteable register:

• shallow history retains the parent and direct active-child values, then runs typed initializers below the remembered boundary
• deep history restores the complete remembered descendant configuration and values
• restoration does not consume the register; the next parent exit overwrites it
• defaults return a typed parent snapshot when no configuration has been captured
• entry actions and invokes run again; prior effects, actors, and timers are not rewound

Machine readiness tracks missing defaults and shallow initializers through the existing staged .handle(...) model. Remembered values are schema-validated at persistence boundaries, including nested and parallel configurations.

Verification

• pnpm check
• 216/216 runtime tests
• 101/101 type tests, 417 assertions
• consumer package validation
• package verification

Dedicated coverage includes defaults, exact deep restoration, shallow fresh initialization, overwrite/not-stack behavior, multiple history registers, parallel and nested-parallel restoration, same-microstep parent exit/reentry, lifecycle ordering, effectful initializers, and corrupt persisted paths/values.

The adversarial suite exposed a nested-parallel ancestor-value bug during development; the final scoped-history target preserves active ancestors and unaffected parallel sibling regions.

Type performance

Measured with TypeScript 6.0.3 and skipLibCheck=true:

Scenario	Before	After	Total change	Marginal change
Machine.defineStates	2,883	2,894	+11 (+0.4%)	+11
Machine.make	7,838	8,334	+496 (+6.3%)	+485 (+9.8%)
machine.handle	17,314	19,389	+2,075 (+12.0%)	+1,579 (+16.7%)

A bounded optimization pass kept active/history filtering and readiness analysis intact. Further reduction would require weakening the filtered API or materially restructuring handler-topology analysis.