chore(ci): add lint+format PR gate, reusable template, and consolidate Node 24

[MiguelLZPF]

Description

Adds a PR-time CI gate that runs npm run <module>:format:check && npm run <module>:lint for ATS and Mass Payout independently, plus the related CI housekeeping required to make the gate land cleanly.

Highlights

• New workflows 103-flow-ats-lint.yaml and 104-flow-mp-lint.yaml — trigger on PRs touching their respective module paths.
• Reusable template 800-call-lint-format.yaml (Hiero [CALL] 800-prefix) — both 103 and 104 are thin shells that delegate to it.
• Always full-tree mode — deterministic, mirrors the local npm run <module>:lint contract. Delta-mode scripts kept in package.json for local dev only.
• Node centralised to .nvmrc (24.15.0 — current Active LTS, exact-patch pin) via node-version-file: in every setup-node step. Drops 11 hard-coded node-version: 22.20.0 references.
• Obsolete NODE_OPTIONS=--max-old-space-size=... heap bumps removed across package.jsons and workflow env: blocks. They pre-date the lib-based architecture migration and are no longer required (verified: contracts/sdk/web build green, web tests pass).
• Workflow name: prefixes aligned with filenames — fixes 6 deviant entries (e.g. 001-flow-pull-request-formatting.yaml previously declared "000: [FLOW]"). Hiero naming is now consistent across all 11 workflows.
• Runner consolidation — 300/301 switched from ubuntu-latest to token-studio-linux-medium for parity with the rest of the repo.
• @typescript-eslint/no-dupe-class-members enabled in MP SDK eslint config (TS-aware variant; the base no-dupe-class-members misreports overload signatures).

Lint debt cleanup (Commit 2)

The new gate would have failed on day-one because of pre-existing latent debt that lint-staged never surfaced (it only checks staged files). Addressed alongside:

• ATS web — 22 errors → 0 (16 files: removed unused vars/expressions, bare catch {} for unused caught errors, let → const, removed test.only debug leftover, fixed two expect(...) calls missing matchers, two duplicate test titles).
• ATS SDK — 16 errors → 0 (12 files: stale eslint-disable for removed rule names purged, bare catch, unused vars/imports/createMock removed, unused expressions converted to if).
• MP frontend — 14 errors → 0 (8 files: bare catch, unused destructure removed, prefer-const, conditional expect refactored to setup-driven unconditional asserts).
• MP contracts compiled artefacts — scripts/results/*.js removed from tracking (had .ts siblings — accidental check-ins). Added gitignore safety net.

⚠️ Deliberately skipped — must be addressed in a follow-up

Workspace	Errors remaining	Rule
packages/mass-payout/contracts	20	max-len in lifecyclecashflow.test.ts (long it("…") test descriptions)
packages/mass-payout/sdk	4	prettier/prettier in lifeCycleCashFlow/operations/Execute*CommandHandler.ts (long class declarations that prettier flattens past the 120-char limit)

These are length-rule conflicts where prettier's printWidth: 120 and ESLint's max-len: 120 disagree on string literals and long class declarations. 104-flow-mp-lint.yaml will fail until they are resolved. Recommended approaches for the follow-up PR:

1. Wrap the test descriptions using template-literal concatenation (preserves readability), OR
2. Relax max-len to a higher cap for MP (e.g. 140), OR
3. Disable max-len in MP eslint configs and defer entirely to prettier.

This PR intentionally does NOT pick a direction — it surfaces the debt cleanly for a separate decision.

Type of change

• Refactor 🔧
• Bug fix 🐞
• New feature ✨
• Breaking change 💥
• Documentation update 📖

Testing

• npm run ats:format:check → green.
• npm run ats:lint → green (0 errors, 2 pre-existing warnings).
• npm run ats:contracts:build / ats:sdk:build / ats:web:build → green (without NODE_OPTIONS heap bumps).
• npm run ats:web:test → 183/183 passing, 79 snapshots.
• npx jest TabContent.test -t "should pass t function to components" → 1/1 passing (verifies the restored assertion).
• npx prettier --check on all new YAMLs → green.
• npm run mass-payout:format:check → green.
• npm run mass-payout:lint → 24 errors (all length-rule, scoped above).