[RickUsingGitHub]

Step 1 of 2 of the structural clean-up left over from the v1.62 code review. No change in behaviour. Step 2 (splitting js/app.js) follows as its own pull request on top of this one.

What's added

• eslint.config.js (ESLint 10, flat config) suited to the code as it is:
  • js/*.js are linted as classic browser scripts (no modules), with Chart, pdfjsLib and module as the only extra globals. Amber needs none: each file declares it.
  • tests/unit-*.js, scripts/ and the config files are CommonJS; the Playwright specs get Node and browser globals.
  • ESLint's recommended set, plus no-unused-vars, no-shadow, no-var, prefer-const, eqeqeq, and the house style from @stylistic/eslint-plugin: 4-space indent, single quotes, semicolons.
• eslint-rules/no-extra-arguments.js, a small rule of the project's own. ESLint has nothing built in for a call that passes more arguments than the function takes, which is what the demandMonthsHtml leftover was. It checks functions, and Amber.* functions, defined in the same file, and leaves alone anything with ...rest, arguments or a spread call.
• npm run lint, and a lint step in .github/workflows/test.yml (straight after npm ci, so it fails before the browsers are installed).
• tests/unit-syntax.js, now first in the unit run. It parses every js/*.js (no other unit script loads help.js, app.js and the other DOM files), and checks that index.html loads each of them once, with app.js last. That second check is there for the split in step 2.

What it found, and what was done

Finding	Where	Fix
Unused amberRates	computePlanTotals (js/costs.js)	Removed
Unused perKwh	precalculateDailySummaries and also channelPeriodBreakdown (js/costs.js)	Removed
A second argument the function ignores	demandMonthsHtml(…, 'demandDays'), twice (js/app.js)	Removed
Shadowed money (four functions had their own, under a file-level one)	js/app.js	The file-level one was only used by displayResults, so it moved in there. Each function keeps its own formatter, unchanged
Shadowed th, d; an initial null never read	js/planner-ui.js	The inner th gave the same output as the outer one, so it went; d renamed
Shadowed sum; unused n	planYear, simulateBattery (js/planner.js)	Renamed to weighted; removed
Unused id	js/calendar.js	Object.values instead of Object.entries
A raw byte-order mark inside a regex literal	js/estimate.js, js/import.js	Written as `` (the same character, but an editor can't strip it)
let that never changes (7)	several	const
Unused helpers	nem12, planner, ui specs; a shadowed name in unit-planner.js	Removed or renamed. No assertion changed

Rules tuned rather than code restyled

• The tests keep their own alignment of long assert conditions and tables of cases (indent checks for call arguments and arrays are off under tests/).
• preserve-caught-error is off: network errors are replaced on purpose by a plain message.
• One eslint-disable-next-line in js/redispatch.js, on a tally that isn't read again but should stay right if a step is added after it.

Checks

• npm run lint: clean.
• npm run test:unit: passes (383 ok lines).
• Playwright: 66 of 66 pass, the same 66 as on main before the change.
• npm run build:css leaves css/app.css unchanged.
• Version bumped to 1.63 in index.html, js/constants.js and tests/unit-time.js; README.md, CLAUDE.md and docs/ updated.

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Generated by Claude Code