Apply upstream security hardening (parent PR #29) to fork

[cbeaulieu-gt]

Summary

This fork (cbeaulieu-gt/claude-code-cli-ui) is missing the security hardening drafted in the parent repo Ngxba/claude-code-cli-ui PR Ngxba#29 ("harden security — patch 7 critical and 3 high vulnerabilities"). Parent PR Ngxba#29 is still open/unmerged upstream, so a normal upstream-master merge does not deliver the fixes. Plan: cherry-pick the PR Ngxba#29 head branch (fix/security-hardening, single commit e25420e8) onto a feature branch of this fork, resolve conflicts, and ship all fixes in one PR.

Vulnerabilities patched

Sev	Issue	File(s)
Critical	Command injection via exec()	server/api/reveal.post.ts
Critical	Arbitrary file read (no path restriction)	server/api/files.get.ts
Critical	Arbitrary directory listing	server/api/directories.get.ts
Critical	Hardcoded bypassPermissions SDK mode	server/utils/claudeSdk.ts, server/utils/providers/claudeProvider.ts
Critical	XSS — v-html sinks without sanitizer	app/utils/markdown.ts, app/utils/messageFormatting.ts
Critical	MCP import writes arbitrary configs	server/api/mcp/import.post.ts
High	Path traversal via agent slugs	server/utils/agentUtils.ts
High	Debug endpoint leaks process.env.PATH	server/api/debug/claude-cli.get.ts
High	Orphaned PTY processes on shutdown	server/utils/cliSession.ts

Adds server/utils/path-security.ts, dompurify (+ types), and a vitest test suite (tests/security/*, vitest.config.ts).

Known conflicts vs current master

merge-tree against master (HEAD 4649427) predicts conflicts in:

• package-lock.json (regenerate)
• server/utils/providers/claudeProvider.ts (this fork's MCP transport/capability work overlaps the bypassPermissions fix)

Acceptance criteria

• All 18 files from PR fix: harden security — patch 7 critical and 3 high vulnerabilities Ngxba/claude-code-cli-ui#29 applied to fork
• claudeProvider.ts conflict resolved preserving both the MCP transport work and the 'default' permission-mode fix
• package-lock.json regenerated cleanly
• bun run typecheck passes
• bun run build succeeds
• Security test suite (vitest) passes
• PR opened against fork master

🤖 Generated by Claude Code on behalf of @cbeaulieu-gt