Support on_project_first_start lifecycle hook (tmuxinator parity)

Feature Request

tmuxinator supports on_project_first_start — a lifecycle hook that fires only on first session creation, not on subsequent starts when the session already exists.

tmuxinator reference

From ~/study/ruby/tmuxinator/lib/tmuxinator/hooks/project.rb:17-20 and template.erb:16-22:

<%- if append? || !tmux_has_session?(name) -%>
  # First start path — on_project_first_start fires here
  <%= hook_on_project_first_start %>
  # ... create session ...
<%- else -%>
  # Restart path — on_project_restart fires here
<% end %>

The hook fires when !tmux_has_session?(name) — i.e., only when the session doesn't already exist.

Use case

on_project_first_start: rake db:create && rake db:migrate
on_project_restart: rake db:migrate
on_project_start: echo "starting"

• First tmuxinator start: runs db:create && db:migrate (first start) + echo starting (always)
• Subsequent tmuxinator start: runs db:migrate (restart) + echo starting (always)

Current state

• The tmuxinator importer now passes on_project_first_start through with a warning (commit da089cc6)
• The builder does not yet implement this hook
• tmuxp has on_project_start (fires always) and on_project_restart (fires when session exists)

Implementation

In src/tmuxp/cli/load.py, the session-exists check at line 716 already distinguishes new vs existing sessions. The on_project_first_start hook should fire in the "new session" path (line 744) but NOT in the "session exists" path (line 716).

Files

• src/tmuxp/cli/load.py — fire hook in new-session path only
• src/tmuxp/workspace/loader.py — add to hook expansion list
• src/tmuxp/workspace/importers.py — remove warning (already passes through)

Start in src/tmuxp/cli/load.py at the session-exists check around lines 716 and 744, then inspect hook expansion in src/tmuxp/workspace/loader.py. Update src/tmuxp/workspace/importers.py where the pass-through warning is handled. Done means the hook runs only for a new session, not an existing one, while the other lifecycle hooks retain their behavior.