feat(chat): project-scoped chat — mcpctl chat --project <name>

Chat directly with a Project (no Agent needed): its Prompts become the system
context, its MCP-server tools are callable, its llmProvider/llmModel drive the
LLM, and (opt-in) the model can read secret values. History is saved inside the
project, attributed per user, resumable, and deletable (RBAC-permitting) — "use
it like Claude, scoped to the project".

Backend (reuses the agent-chat orchestrator):
- ChatThread is now agent-XOR-project (schema + migration + CHECK constraint);
  new listThreadsByProject / deleteThread on the repo.
- ChatService: prepareProjectContext (project prompt + Prompts by priority,
  llm from llmProvider with llmModel override, project tools), shared
  runChatLoop/runChatStreamLoop, project thread CRUD with owner enforcement
  (404-not-403 on foreign threads), admin-override delete.
- Gated get_secret virtual tool: offered only with --allow-secrets AND the
  caller's view:secrets; resolves via SecretService, never routes to a server.
- routes/project-chat.ts (chat SSE+non-stream, threads create/list/delete);
  RBAC run:projects:<name>.

CLI:
- `mcpctl chat --project <name>` (+ --allow-secrets), one-shot/REPL/resume.
- REPL /threads, /resume <id>, /delete <id>; project-aware header + /tools.
- `mcpctl get threads --project <name>`, `mcpctl delete thread <id> --project`.
- completions regenerated (--project completes project names).

Tests: 8 new project-chat unit tests; full mcpd (945) + CLI (508) green;
schema validated against Postgres. Docs: docs/chat.md "Project chat" section.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

completions/mcpctl.bash

@@ -245,9 +245,9 @@ _mcpctl() {
       if [[ $((cword - subcmd_pos)) -eq 1 ]]; then
         local names
         names=$(_mcpctl_resource_names "agents")
-        COMPREPLY=($(compgen -W "$names -m --message --thread --system --system-file --system-append --personality --temperature --top-p --top-k --max-tokens --seed --stop --allow-tool --extra --no-stream -h --help" -- "$cur"))
+        COMPREPLY=($(compgen -W "$names -p --project --allow-secrets -m --message --thread --system --system-file --system-append --personality --temperature --top-p --top-k --max-tokens --seed --stop --allow-tool --extra --no-stream -h --help" -- "$cur"))
       else
-        COMPREPLY=($(compgen -W "-m --message --thread --system --system-file --system-append --personality --temperature --top-p --top-k --max-tokens --seed --stop --allow-tool --extra --no-stream -h --help" -- "$cur"))
+        COMPREPLY=($(compgen -W "-p --project --allow-secrets -m --message --thread --system --system-file --system-append --personality --temperature --top-p --top-k --max-tokens --seed --stop --allow-tool --extra --no-stream -h --help" -- "$cur"))
       fi
       return ;;
     chat-llm)