fix(project): avoid password file reads in dry-run update

[JerryNee]

Summary

• keep project update --dry-run from reading --password-file before the dry-run preview
• compute updatedFields from supplied flags, then resolve password file contents only on the real PATCH path
• add unit and subprocess regression coverage for a missing password file under dry-run

Repro

Before this change, testsprite project update proj_anything --password-file /tmp/missing --dry-run --output json exited 1 with a raw ENOENT, even though dry-run is documented to skip filesystem writes/reads. After this change it exits 0 and previews updatedFields: ["password"].

Verification

• npm test -- src/commands/project.test.ts
• npm test -- test/cli.subprocess.test.ts
• npm run typecheck
• npm run lint
• npm test
• npm run build
• node dist/index.js project update proj_anything --password-file /tmp/definitely-not-here-testsprite --dry-run --output json