chore: add just launcher

[ovitrif]

This PR adds a Just command launcher for common local Android development tasks.

Description

This PR:

1. Adds a top-level Justfile with short commands for setup, build, test, lint, just run, release, E2E, translations, changelog preview, and cleanup.
2. Adds an .env.example template and just init for creating the ignored local .env file.
3. Updates README, agent rules and release command docs to route thru the Just launcher.
4. Hardens translation pull cleanup so pulled XML markup is fixed and malformed XML fails fast.

Preview

N/A

QA Notes

Manual Tests

N/A

Automated Checks

• just init
• just list
• just --dry-run run
• just --dry-run release
• just --dry-run test file LightningRepoTest
• just --dry-run test lane ComposeUi
• just --dry-run translations pull
• just --dry-run translations push source
• just --dry-run translations push all
• just --dry-run translations push exits with usage
• Fresh temp worktree: just translations pull
• Fresh temp worktree: parsed all pulled values*/strings.xml files with Python XML parser
• Fresh temp worktree with stubbed tx: just translations push source and just translations push all
• Fresh temp worktree with stubbed tx: bare just translations push exits with usage
• just --dry-run e2e network assembleTnetRelease
• just --dry-run e2e no geo
• just compile
• just test
• just lint
• just build
• Just 1.51.0 formatter: just --unstable --fmt --check

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: d317acecb9

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[ben-kaufman]

Looks good to me.

[ovitrif]

Looks good to me.

Thanks 🙏🏻

I'm not certain the translation commands work at all. Last time I checked them they didn't work (test on fresh clone), and IIRC Phil also signalled they didn't work for him.
So my plan is do a round of local runs of these commands manually and still iterate as needed, hope I can squeeze a fix for those in here as well as needed 🤞

[ovitrif]

Checked this from a fresh temp worktree.

Results:

• just translations pull reaches Transifex and completes, but currently pulls content changes for values-b+es+419, values-es-rES, and values-pt-rBR.
• The pull exposed a real pre-existing issue: Transifex can return half-escaped markup like <accent&gt;, which made pulled XML malformed.
• Fixed the pull cleanup to repair that markup before validation and to fail if any pulled strings.xml remains malformed.
• Verified all pulled values*/strings.xml files parse after the fix.
• Verified just translations push and just translations push source with a stubbed tx so the local rename/restore workflow is tested without mutating Transifex.

Updated in and force-pushed.