What does this PR do?

PR #14914 introduced _web_ui_build_needed() to skip the npm install + Vite rebuild when the dist is already fresh. However, it contains a path bug that makes the fix a complete no-op:

# PR #14914 — WRONG
sentinel = web_dir / "dist" / ".vite" / "manifest.json"

web_dir is PROJECT_ROOT/web/. But vite.config.ts sets:

build: { outDir: "../hermes_cli/web_dist" }

So the actual build output lands in hermes_cli/web_dist/, never in web/dist/. The sentinel is always missing → _web_ui_build_needed always returns True → the full npm build runs on every startup → OOM on low-memory VPS is unchanged.

This PR fixes the sentinel path:

# Correct — matches actual Vite outDir
dist_dir = web_dir.parent / "hermes_cli" / "web_dist"
sentinel = dist_dir / ".vite" / "manifest.json"

Related Issues

Fixes #14898
Supersedes / fixes the regression in #14914

Changes

• hermes_cli/main.py: _web_ui_build_needed() uses web_dir.parent / "hermes_cli" / "web_dist" as dist_dir
• tests/hermes_cli/test_web_ui_build.py: 11 tests including a dedicated regression test (test_web_dist_dir_not_web_dist_subdir) that would have caught the fix(cli): skip web UI rebuild when dist/ is present and sources are unchanged #14914 bug

How to Test

pytest tests/hermes_cli/test_web_ui_build.py -v
# 11 passed

End-to-end: run hermes dashboard once to build, then run again — second startup skips npm entirely.