feat(cli): add setup ide prophet command and docs

[clavery]

Summary

• add new b2c setup ide topic and b2c setup ide prophet command
• generate a Prophet-compatible dw.js bridge script that resolves config via b2c setup inspect --json --unmask
• make generated script export via module.exports = dwJson, include runtime diagnostics, and safely fall back to dw.json
• support runtime root resolution for Prophet extension contexts (SFCC_WORKING_DIRECTORY, SFCC_CONFIG, __dirname, module.filename, workspace, cwd)
• add IDE Integration guide page and CLI reference updates
• update skill docs for the new setup flow
• add changeset for @salesforce/b2c-cli

Verification

• pnpm --filter @salesforce/b2c-cli run test:agent
• pnpm --filter @salesforce/b2c-cli run typecheck:agent
• pnpm --filter @salesforce/b2c-cli exec eslint src/commands/setup/ide/prophet.ts test/commands/setup/ide/prophet.test.ts
• pnpm exec prettier --check packages/b2c-cli/src/commands/setup/ide/prophet.ts packages/b2c-cli/test/commands/setup/ide/prophet.test.ts docs/guide/ide-integration.md docs/cli/setup.md