fix(cli): accept capacitor.config.js as a --capacitor-config target

[posthog-eu]

Summary

Monorepo apps whose config is capacitor.config.js couldn't use the new --capacitor-config flag at all — the CLI rejected the path before doing any work.

Problem

• The --capacitor-config validator (cli/src/config/index.ts) matched only .ts/.json, so capacitor.config.js was rejected with …must point to a capacitor.config.*.ts or capacitor.config.*.json file, which reads like a wrong path rather than an unsupported extension.
• capacitor.config.js is a first-class config for Capacitor itself and is already in init's own capacitorConfigFiles list, so the exclusion was inconsistent.

Changes

• Accept .js in the extension regex and name all three extensions in the error message.
• loadConfigTarget gets a .js branch that require()s the file, mirroring Capacitor's own capacitor.config.js loader.
• Add JS write support. Capacitor's writeConfig only formats .ts/.json and silently no-ops on .js, so simply widening the regex would trade a clear error for a silent failed write. writeConfigTarget now emits CommonJS itself via Capacitor's formatJSObject, matching how Capacitor renders .ts.

.mjs/.cjs are intentionally left out: Capacitor never loads them as configs and the writer emits CommonJS, so allowing them would let reads pass but writes silently no-op.

Test plan

• Extended cli/test/test-capacitor-config-target.mjs:
  • resolveCapacitorConfigTargetPath now accepts a capacitor.config.js target and still rejects .mjs.
  • loadConfigForWrite reads a capacitor.config.js target correctly.
  • A real CLI write (capgo app setting … --capacitor-config <capacitor.config.js>) updates the JS file, preserves app-scoped plugins, and leaves the root config untouched.
• bun run lint, bun run typecheck, bun run build, and bun run test:init-monorepo-targeting all pass.

Screenshots

n/a — CLI validation/serialization change; covered by the test above.

Checklist

• My code follows the code style of this project and passes bun run lint:backend && bun run lint.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• My change has adequate E2E test coverage.
• I have tested my code manually, and I have provided steps how to reproduce my tests.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 43 untouched benchmarks
⏩ 2 skipped benchmarks¹

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_{Comparing posthog-self-driving/fixcli-accept-capacitorconfigjs-as-a-53cffc (a97a128) with main (60a641e)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud