Add planner-backed devtools simulation

[SandroMaglione]

Summary

• Add isolated planner-backed simulation sessions to the interactive text-tree visualizer.
• Generate machine and event controls from Effect schemas, including visible field metadata and inline validation errors.
• Show state changes, microsteps, selected branches, raised and emitted events, planned commands, completion, and output without committing side effects.

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 type and runtime performance smoke tests passed. The schema-derived forms, authoritative field errors, and Idle -> Finished planner trace were also verified in the local browser.

[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)	0.08s	0.08s
Machine.make (3 states, 2 events)	0.13s	0.13s
machine.handle (3 states, 2 transitions)	0.21s	0.21s
fluent transition (10 named branches)	0.45s	0.46s
fluent invocation (state-dependent Effect)	0.46s	0.44s
machine.handle (depth 24)	0.65s	0.64s
machine.handle (wide depth 16)	0.67s	0.65s
machine.handle (parallel/history/choice)	0.54s	0.55s
machine definition (3 independent implementations)	0.53s	0.57s
machine exact input/output/error/services	0.50s	0.52s
execution adapter readiness	0.51s	0.51s

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	110,768 transitions/s
Drain burst with terminal fence	334,163 increments/s
Drain burst with a change observer	313,626 increments/s
Lookup and send to one child	280,209 increments/s
Start and stop a machine	135,980 machines/s
Start and stop a parent with one child	27,780 families/s
Plan transitions through a compound state	95,350 transitions/s
Plan transitions through parallel regions	78,685 transitions/s
Drain burst through a compound state	279,692 events/s
Drain burst through two parallel regions	280,942 events/s
Drain a compound-state burst with a change observer	266,606 events/s

Process runtime reference points

Scenario	Effect Machine
Start and stop a raw generic process	15,434 processes/s
Start and stop a raw compiled process	61,843 processes/s

Memory profile	Effect Machine
Idle machine	1.8 KiB
Raw generic managed process	13.9 KiB
Raw compiled process	3.2 KiB
Two independent idle machines	3.4 KiB
Idle parent with one child	5.8 KiB
Parent with observed child registry	10.0 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	112,547 transitions/s	2.0% MAD	110,768 transitions/s	2.1% MAD	-1.6%
Drain burst with terminal fence	338,966 increments/s	0.4% MAD	334,163 increments/s	2.8% MAD	-1.4%
Drain burst with a change observer	320,181 increments/s	0.2% MAD	313,626 increments/s	3.0% MAD	-2.0%
Lookup and send to one child	283,802 increments/s	0.4% MAD	280,209 increments/s	2.9% MAD	-1.3%
Start and stop a machine	134,517 machines/s	0.7% MAD	135,980 machines/s	1.1% MAD	+1.1%
Start and stop a parent with one child	28,276 families/s	2.6% MAD	27,780 families/s	1.0% MAD	-1.8%
Plan transitions through a compound state	96,483 transitions/s	1.3% MAD	95,350 transitions/s	2.3% MAD	-1.2%
Plan transitions through parallel regions	78,838 transitions/s	2.9% MAD	78,685 transitions/s	2.6% MAD	-0.2%
Drain burst through a compound state	286,306 events/s	0.7% MAD	279,692 events/s	0.3% MAD	-2.3%
Drain burst through two parallel regions	286,780 events/s	1.5% MAD	280,942 events/s	1.0% MAD	-2.0%
Drain a compound-state burst with a change observer	272,815 events/s	0.9% MAD	266,606 events/s	1.5% MAD	-2.3%
Idle machine heap per unit	1.8 KiB	0.1% MAD	1.8 KiB	0.0% MAD	-0.2%
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	0.4% MAD	3.2 KiB	0.9% MAD	+0.6%
Two independent idle machines heap per unit	3.4 KiB	0.0% MAD	3.4 KiB	0.0% MAD	-0.0%
Idle parent with one child heap per unit	5.8 KiB	0.0% MAD	5.8 KiB	0.0% MAD	+0.0%
Parent with observed child registry heap per unit	10.0 KiB	0.0% MAD	10.0 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	15,970 processes/s	0.7% MAD	15,434 processes/s	1.5% MAD	-3.4%
Start and stop a raw compiled process	62,267 processes/s	0.6% MAD	61,843 processes/s	0.8% MAD	-0.7%

Regression guard

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

Versions and interpretation

• Effect Machine: 0.23.0

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.