Add machine acceptance queries and atom factories

[SandroMaglione]

Summary

• add Machine.can in direct and machine-specialized forms, with public event decoding, hierarchy-aware declinable selection, and no transition lifecycle execution
• add unbound and runtime-bound AtomMachine.factory constructors that preserve startup input arity and exact bridge error channels while creating fresh lazy bridges
• document direct construction, reusable constructors, keyed identity, and the derived-atom React composition for concrete event acceptance

Changeset

• Added or updated for a library or package-metadata change
• Not required because this PR does not change a publishable package

Validation

• pnpm check
• Automated type-performance measurement passed or was not required
• Automated runtime- and memory-performance measurement passed or was not required

Local pnpm perf:types and pnpm perf:runtime smoke tests passed. The pull request workflows provide the authoritative base-versus-PR comparisons.

[github-actions]

Type performance

Measured with TypeScript 6.0.3 and skipLibCheck=true.

Scenario	Base	PR	Difference
Effect only	55	55	0 (0.0%)
Import effect-machine	55	55	0 (0.0%)
Machine.states (3 states)	3,039	3,039	0 (0.0%)
Machine.make (3 states, 2 events)	10,787	10,787	0 (0.0%)
machine.handle (3 states, 2 transitions)	28,551	28,551	0 (0.0%)
fluent transition (10 named branches)	122,775	122,775	0 (0.0%)
fluent invocation (state-dependent Effect)	108,429	108,429	0 (0.0%)
machine.handle (depth 24)	207,970	207,970	0 (0.0%)
machine.handle (wide depth 16)	236,332	236,332	0 (0.0%)
machine.handle (parallel/history/choice)	144,812	144,812	0 (0.0%)
machine definition (3 independent implementations)	143,617	143,617	0 (0.0%)
machine exact input/output/error/services	129,873	129,873	0 (0.0%)
execution adapter readiness	136,469	136,469	0 (0.0%)

Marginal instantiations are measured against the matching setup without that API call:

Scenario	Base	PR	Difference
Import effect-machine	0	0	0
Machine.states (3 states)	2,984	2,984	0 (0.0%)
Machine.make (3 states, 2 events)	7,740	7,740	0 (0.0%)
machine.handle (3 states, 2 transitions)	17,764	17,764	0 (0.0%)
fluent transition (10 named branches)	112,498	112,498	0 (0.0%)
fluent invocation (state-dependent Effect)	99,018	99,018	0 (0.0%)
machine.handle (depth 24)	187,474	187,474	0 (0.0%)
machine.handle (wide depth 16)	217,043	217,043	0 (0.0%)
machine.handle (parallel/history/choice)	124,167	124,167	0 (0.0%)
machine definition (3 independent implementations)	127,576	127,576	0 (0.0%)
machine exact input/output/error/services	115,217	115,217	0 (0.0%)
execution adapter readiness	106,299	106,299	0 (0.0%)

Check times (informational)

Scenario	Base	PR
Effect only	0.02s	0.02s
Import effect-machine	0.02s	0.02s
Machine.states (3 states)	0.07s	0.07s
Machine.make (3 states, 2 events)	0.12s	0.12s
machine.handle (3 states, 2 transitions)	0.19s	0.19s
fluent transition (10 named branches)	0.43s	0.42s
fluent invocation (state-dependent Effect)	0.41s	0.40s
machine.handle (depth 24)	0.62s	0.61s
machine.handle (wide depth 16)	0.62s	0.63s
machine.handle (parallel/history/choice)	0.50s	0.50s
machine definition (3 independent implementations)	0.51s	0.52s
machine exact input/output/error/services	0.46s	0.46s
execution adapter readiness	0.47s	0.48s

Type instantiations are the comparison metric. Check time varies with runner load and is informational only.

[github-actions]

Runtime performance

Median of 5 independent benchmark processes on AMD EPYC 7763 64-Core Processor with Node v24.19.0.

Pull request baseline

Scenario	Effect Machine
Plan counter transitions	123,362 transitions/s
Drain burst with terminal fence	387,539 increments/s
Drain burst with a change observer	364,011 increments/s
Lookup and send to one child	316,716 increments/s
Start and stop a machine	142,187 machines/s
Start and stop a parent with one child	29,400 families/s
Plan transitions through a compound state	104,986 transitions/s
Plan transitions through parallel regions	87,331 transitions/s
Drain burst through a compound state	307,522 events/s
Drain burst through two parallel regions	305,927 events/s
Drain a compound-state burst with a change observer	292,063 events/s

Process runtime reference points

Scenario	Effect Machine
Start and stop a raw generic process	15,046 processes/s
Start and stop a raw compiled process	60,972 processes/s

Memory profile	Effect Machine
Idle machine	1.7 KiB
Raw generic managed process	13.9 KiB
Raw compiled process	3.1 KiB
Two independent idle machines	3.3 KiB
Idle parent with one child	5.7 KiB
Parent with observed child registry	9.8 KiB
Parent with observed invoked child snapshots	6.3 KiB

Effect Machine change from base

Metric	Base	Base variability	PR	PR variability	Difference
Plan counter transitions	122,396 transitions/s	0.4% MAD	123,362 transitions/s	0.2% MAD	+0.8%
Drain burst with terminal fence	389,706 increments/s	0.1% MAD	387,539 increments/s	1.4% MAD	-0.6%
Drain burst with a change observer	362,867 increments/s	0.6% MAD	364,011 increments/s	1.5% MAD	+0.3%
Lookup and send to one child	319,198 increments/s	0.9% MAD	316,716 increments/s	1.6% MAD	-0.8%
Start and stop a machine	142,389 machines/s	1.0% MAD	142,187 machines/s	0.9% MAD	-0.1%
Start and stop a parent with one child	28,682 families/s	0.2% MAD	29,400 families/s	1.7% MAD	+2.5%
Plan transitions through a compound state	105,809 transitions/s	0.7% MAD	104,986 transitions/s	1.3% MAD	-0.8%
Plan transitions through parallel regions	88,058 transitions/s	0.7% MAD	87,331 transitions/s	1.2% MAD	-0.8%
Drain burst through a compound state	317,787 events/s	1.1% MAD	307,522 events/s	1.1% MAD	-3.2%
Drain burst through two parallel regions	319,288 events/s	0.7% MAD	305,927 events/s	1.9% MAD	-4.2%
Drain a compound-state burst with a change observer	300,121 events/s	0.1% MAD	292,063 events/s	1.2% MAD	-2.7%
Idle machine heap per unit	1.7 KiB	0.2% MAD	1.7 KiB	0.1% MAD	+0.1%
Raw generic managed process heap per unit	13.9 KiB	0.0% MAD	13.9 KiB	0.0% MAD	-0.0%
Raw compiled process heap per unit	3.1 KiB	0.0% MAD	3.1 KiB	0.1% MAD	+0.1%
Two independent idle machines heap per unit	3.3 KiB	0.0% MAD	3.3 KiB	0.0% MAD	-0.0%
Idle parent with one child heap per unit	5.7 KiB	0.0% MAD	5.7 KiB	0.0% MAD	+0.0%
Parent with observed child registry heap per unit	9.8 KiB	0.0% MAD	9.8 KiB	0.0% MAD	-0.0%
Parent with observed invoked child snapshots heap per unit	6.3 KiB	0.0% MAD	6.3 KiB	0.0% MAD	-0.0%

Process runtime reference change from base

Metric	Base	Base variability	PR	PR variability	Difference
Start and stop a raw generic process	15,288 processes/s	0.3% MAD	15,046 processes/s	0.3% MAD	-1.6%
Start and stop a raw compiled process	61,046 processes/s	0.4% MAD	60,972 processes/s	1.4% MAD	-0.1%

Regression guard

No large, noise-adjusted throughput or heap regressions detected.

Versions and interpretation

• Effect Machine: 0.29.0

Higher throughput is better; lower heap is better. Variability is the median absolute deviation across independent processes, relative to their median. Small differences on shared GitHub-hosted hardware remain informational; the required guard rejects only large changes beyond the measured noise allowance.