feat: add npx oma-forge CLI and simplify workflow authoring

[ibrahimkzmv]

What

Adds the oma-forge CLI (npx oma-forge <workflow.ts>) to start the Forge API and UI against any workflow file, and simplifies workflow authoring: default-export functions, forgeHooks() / forgeAbortSignal(), and a reporter run-workflow shim instead of bootstrapForgeWorkflow + ForgeRunContext.

packages/cli — spawns server + Vite, sets FORGE_WORKFLOW_PATH / FORGE_PROJECT_ROOT, opens browser
Server — resolveProjectRoot(), workflow runner uses @oma-forge/reporter/run-workflow
Reporter — forgeHooks(), runForgeWorkflow, deprecated bootstrapForgeWorkflow
README — npx oma-forge docs + updated workflow example

Why

Developers should point Forge at their workflow and debug in the UI without cloning the monorepo or hand-wiring bootstrap boilerplate. Workflows should keep using OpenMultiAgent directly with minimal Forge-specific surface area.

Checklist

• npm run lint passes
• npm test passes
• Added/updated tests for changed behavior (workflow-paths.test.ts, CLI parse-args tests)
• No new runtime dependencies (or justified in the PR description) — CLI depends on existing workspace packages only; no new third-party runtime deps