refactor: derive platform allow-lists from the canonical device tuples

[thymikee]

What

The set of supported platforms was hand-restated in three places that must agree:

1. The canonical tuples in src/utils/device.ts (PLATFORMS / PLATFORM_SELECTORS).
2. The --platform flag's enumValues in src/utils/cli-flags.ts.
3. The leaf-platform validation in normalizeOpenDevice in src/client-normalizers.ts.

This PR makes copies (2) and (3) derive from the canonical source so they cannot drift.

• Export PLATFORMS from device.ts and add an isPlatform() leaf-platform type guard derived from it. isPlatform accepts exactly PLATFORMS and rejects the apple selector (which is a routing selector, not a concrete device platform).
• cli-flags.ts --platform: enumValues and usageLabel now derive from PLATFORM_SELECTORS (the CLI accepts the leaf platforms plus the apple selector).
• client-normalizers.ts normalizeOpenDevice: the leaf-platform gate now uses isPlatform(). Per-platform udid/serial identifier shaping is unchanged.

Why

Three independent restatements of the same allow-list invite silent drift when a platform is added or renamed. Deriving the two non-canonical copies from device.ts makes the canonical tuples the single source of truth.

Behaviorless

The derived sets are identical to the previous hardcoded sets:

• --platform enumValues stay ['ios','macos','android','linux','web','apple'].
• normalizeOpenDevice still accepts exactly ['ios','macos','android','linux','web'] and rejects apple/unknown platforms.

New tests assert these memberships explicitly so the derivation is pinned.

Validation

• node_modules/.bin/tsc -p tsconfig.json --noEmit (exit 0)
• node ./node_modules/oxfmt/bin/oxfmt --write <changed .ts files>
• node_modules/.bin/oxlint <changed .ts files> --deny-warnings (exit 0)
• node_modules/.bin/vitest run cli-flags client-normalizers args device (12 files, 197 tests passed)

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Size Report

Metric	Base	Current	Diff
JS raw	1.4 MB	1.4 MB	-43 B
JS gzip	445.2 kB	445.2 kB	-19 B
npm tarball	583.3 kB	583.3 kB	-33 B
npm unpacked	2.0 MB	2.0 MB	-43 B

Startup median (7 runs, lower is better):

Scenario	Base	Current	Diff
CLI --version	27.4 ms	27.5 ms	+0.2 ms
CLI --help	48.1 ms	47.8 ms	-0.3 ms

Top changed chunks:

Chunk	Raw diff	Gzip diff
dist/src/2948.js	-103 B	-42 B

[thymikee]

Reviewed — merge-ready. The derivation is genuinely behaviorless: PLATFORM_SELECTORS equals the old ['ios','macos','android','linux','web','apple'] byte-for-byte, and isPlatform() matches the old !== chain on every probe (incl. undefined/null/''/numbers/apple/windows). The new tests pin both memberships explicitly, and this lines up with the pattern already in use (contracts.ts, remote-config-schema.ts, command-input.ts all consume PLATFORM_SELECTORS). CI is green across typecheck/unit/integration.

One non-blocking follow-up — same drift you're killing, just out of scope here: there's a fourth restatement of the leaf-platform allow-list at src/replay/script.ts:19, REPLAY_METADATA_PLATFORMS. It's typed Exclude<PlatformSelector, 'apple'> (i.e. Platform) but hardcoded as a Set of only ['ios','android','macos','linux'] — it already omits 'web', so a context platform=web line is silently dropped (script.ts:81) even though the type permits it. Worth deriving it from PLATFORMS too, or narrowing the type if web replay is intentionally unsupported.

Residual risk: ~none. Co-edits src/utils/device.ts with #896 (AppleOS) but in independent regions — no correctness coupling and no required merge order; at most a trivial rebase.

[thymikee]

Thanks @thymikee — opened the follow-up in #899. It narrows ReplayScriptPlatform to Exclude<PlatformSelector, 'apple' | 'web'> and derives REPLAY_METADATA_PLATFORMS from the canonical PLATFORM_SELECTORS instead of restating it a 4th time. Behaviorless: context platform=web was already dropped and stays dropped — now intentionally, type-safe, and from a single source. web support remains a separate feature decision. Doesn't depend on this PR.

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2026-06-27 11:49 UTC