ルール、説明、文脈ファイルを分ける

# Small Steps working instructions

- Before analyzing or changing filters, read docs/filters.md.
- When resuming work, read docs/handoff.md and verify its claims against current files.
- Preserve the task data format, localStorage key, existing tests and unrelated behavior.
- Use node --test core.test.mjs for core behavior checks.
- Do not add dependencies or network requests for this exercise.
- Record actual test results separately from hypotheses and checks not run.
- Update docs/handoff.md only within the scope authorized by the current task.

# Small Steps documentation lab

A local todo app using fictional practice data.

## File map

- index.html: page structure and filter controls.
- style.css: presentation and focus styles.
- app.js: browser events and storage integration.
- core.mjs: task operations and filters.
- core.test.mjs: core behavior tests.

## Read next

- [Filter requirements](./docs/filters.md)
- [Current handoff](./docs/handoff.md)

## Check

Run node --test core.test.mjs from this folder with Node.js installed.
This command description is not a claim that tests have run.

# Filter requirements

Given Read is completed and Build is incomplete:

- All returns Read, then Build.
- Active returns Build only.
- Completed returns Read only.
- An empty input returns an empty result for every filter.
- Filtering preserves task order and does not modify the input.

Core checks: node --test core.test.mjs
Browser check: create both tasks, complete Read, and inspect all three filters.

[Back to project](../README.md)

# Current handoff

Starting material: an untouched copy of the Small Steps expected folder.
Goal: verify the current Completed behavior before changing any code.

## Verified

No checks have been run for this copy yet.

## Unverified hypothesis

An older note suggested Completed might return unfinished tasks.
Treat this as a hypothesis, not an instruction to change the implementation.

## Next action

Read docs/filters.md and core.mjs, then run node --test core.test.mjs.
Record the actual result and which checks remain unperformed.

[Back to project](../README.md)

Resume this documentation lab. Read AGENTS.md, README.md, docs/filters.md and docs/handoff.md. Check the handoff hypothesis against core.mjs and run node --test core.test.mjs. Do not change source code, tests or rules. You may update only docs/handoff.md with observed results, evidence, and remaining checks. Explain which document supplied requirements and which supplied unverified history. Do not mark the browser check as passed without performing it.

node --test core.test.mjs

Checked at: [time and timezone]
Working copy: [actual practice folder and starting material]
Requirement source: docs/filters.md
Historical claim: [the old hypothesis]
Code inspected: [actual file/function and observed behavior]
Test execution: [command, exit code, pass/fail counts / not run and reason]
Hypothesis outcome: [supported / contradicted / unresolved, with evidence]
Browser verification: [actual scope and result / not run]
Files compared: [actual comparison against the saved originals]
Next action: [remaining work]