Fix color linting script for cross platform development

[Steve-Mcl]

Description

This pull request refactors the scripts/lint-colors.js script to remove its dependency on the grep command, making it cross-platform. Additionally, the exit method was changed from a noisy throw to a process.exit(1) (see note below)

Linting infrastructure improvements:

• Replaces all uses of the grep shell command in scripts/lint-colors.js with a new cross-platform grepLines function that recursively searches files for patterns, improving compatibility and reliability. (F18d4070L4R4, [1] [2]
• Changes the script's failure handling to use process.exit(1) instead of throwing an error, ensuring proper exit codes in all environments.

Temp Testing (will be deleted after being ran on CI:

* Adds two probe files, frontend/src/__lint_probe__.scss and frontend/src/__lint_probe__.vue, containing intentional lint violations to test the color linting script. [1] [2]
* Adds a probe-only theme token to frontend/src/ui-components/stylesheets/ff-theme-light.scss to test theme parity checks.

THESE WILL BE DELETED BEFORE MERGE

UPDATE: test probes removed - results can be seen here: https://github.com/FlowFuse/flowfuse/actions/runs/28938870171/job/85856315043?pr=7776

NOTE:

The script originally threw a new Error(...) when a lint fail was detected. While it does give a non-zero exit code (an uncaught exception makes node exit with 1) it also dumps a stack trace pointing at lint-colors.js:159, which reads as if the script itself crashed rather than the lint found violations. The output becomes pure noise for someone who just wants to see what they need to fix.

The usual pattern for a CLI/lint tool is a clean exit with exit code e.g. process.exit(1)

BEFORE

.\packages\flowfuse\scripts\lint-colors.js:159
        throw new Error('FlowFuse color-token lint failed.')
        ^

Error: FlowFuse color-token lint failed.
    at run (.\packages\flowfuse\scripts\lint-colors.js:159:15)
    at Object.<anonymous> (.\packages\flowfuse\scripts\lint-colors.js:167:1)
    at Module._compile (node:internal/modules/cjs/loader:1706:14)
    at Object..js (node:internal/modules/cjs/loader:1839:10)
    at Module.load (node:internal/modules/cjs/loader:1441:32)
    at Function._load (node:internal/modules/cjs/loader:1263:12)
    at TracingChannel.traceSync (node:diagnostics_channel:328:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:237:24)
    at Function.executeUserEntryPoint [as runMai

AFTER

FlowFuse color-token lint failed.

# no stack trace ↑ and the exit code is non zero ↓

~/flowfuse (main)
$ echo "exit code: $?"
exit code: 1

Related Issue(s)

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production
• Link to Changelog Entry PR, or note why one is not needed.

Labels

• Includes a DB migration? -> add the area:migration label

[Steve-Mcl]

probe files confirm the corss-platform changes finds color lint errors.

> @flowfuse/flowfuse@2.32.0 lint
> npm-run-all --sequential lint:eslint lint:colors


> @flowfuse/flowfuse@2.32.0 lint:eslint
(node:2440) ESLintEnvWarning: /* eslint-env */ comments are no longer recognized when linting with flat config and will be reported as errors as of v10.0.0. Replace them with /* global */ comments or define globals in your config file. See https://eslint.org/docs/latest/use/configure/migration-guide#eslint-env-configuration-comments for details. Found in /home/runner/work/flowfuse/flowfuse/test/unit/frontend/stores/context.spec.js at line 1.
(Use `node --trace-warnings ...` to show where the warning was created)
> eslint forge frontend test

(node:2440) ESLintEnvWarning: /* eslint-env */ comments are no longer recognized when linting with flat config and will be reported as errors as of v10.0.0. Replace them with /* global */ comments or define globals in your config file. See https://eslint.org/docs/latest/use/configure/migration-guide#eslint-env-configuration-comments for details. Found in /home/runner/work/flowfuse/flowfuse/test/unit/frontend/subscribers/team-channel.subscriber.spec.js at line 1.

> @flowfuse/flowfuse@2.32.0 lint:colors
> node scripts/lint-colors.js


— Banned color references —
<snip for brevity >


— Banned Tailwind utility classes in templates —

<snip for brevity >

— Theme-file parity —

<snip for brevity >

FlowFuse color-token lint failed.
ERROR: "lint:colors" exited with 1.
Error: Process completed with exit code 1.

The follow commits will now remove the probes

The remaining eslint-env CLI warnings will be resolved when #7774 is merged.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 75.38%. Comparing base (3a61885) to head (ad4db66).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #7776   +/-   ##
=======================================
  Coverage   75.38%   75.38%           
=======================================
  Files         428      428           
  Lines       22539    22539           
  Branches     5944     5944           
=======================================
  Hits        16992    16992           
  Misses       5547     5547           

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