fix: empty response handling, /no_think model gating, per-model profiles

- Detect empty LLM responses (no content, no tool calls) instead of
  silently treating them as task completion. Retries once without tools
  before warning the user.
- Gate /no_think system message and chat_template_kwargs to Qwen/QwQ
  models only — sending /no_think to llama3.x caused empty responses.
- Add model_profiles config section for per-model overrides (token
  budget, thinking, temperature, max_tokens) matched by name prefix.
  Applied at startup and on /model switch.
- Update SessionManager on /model switch so session files record the
  correct model.
- Add NDJSON fallback in SSE stream parser for Ollama compatibility.
- Improve read_file error to suggest find_files on FileNotFoundError.
- Add diagnostic logging for empty streams and empty results.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/tweaks.md

@@ -1,21 +1,12 @@
-Pressing up should cycle history like claude code.
+# UI Issues
+on /clear we need to reset the token counter in the header panel.
 
-~~Remove the user's input from output "you" - it's not needed.~~ Brought back as a condensed one-liner (first line + line count for multi-line).
+# Bugs
 
-Smart shell auto-approve: auto-approve `run_command` when the base executable is in the `allowed_commands` list and the full command doesn't match any `denied_commands` prefix. Only prompt the user for commands whose base executable is unlisted. Currently all shell commands prompt regardless, which is tedious for safe read-only commands like `git branch` or `ls`. The allow/deny lists in `ShellToolConfig` already define what's safe — the permissions service just needs to be shell-aware.
+# Improvements
+add -p to command line args so that the agent can run the prompt and return data directly via STDOUT
 
-Show a token count or some other display for when the model is "thinking" for a long period of time. I want a way for the user to know the model is working on it.
+# Open questions:
+How might we pass a directory to this app and have it use that directory as it's workspace so I don't have to copy files or do odd things to work in other directories.
 
-/models command to show models available and temporarly change models in the session
-
-pass a directory to the tool so that it uses that directory as it's root for commands.
-
-add a skills directory so we can prompt our own skills for the tool to use similar to Claude Code
-
-need not only a session log, but also a log of what the llm is thinking and how it's working somehow. I need a way to see behind the curtain.
-
-# Left of from Phase 7 of old roadmap - finish these first
-- Permission modal auto-approves (TODO: proper modal dialog)
-- Session resume auto-resumes (TODO: modal y/n)
-- LLM client cleanup on unmount not yet wired
-- No automated TUI tests (Textual's AppTest can be added later)
+How do we handle huge files not taking up so many tokens?