feat: live Jupyter session introspection + CRLF/LF install fix

[KadenMc]

Adds aexp.jupyter for live introspection of the connected kernel:

• init()/whoami() return a SessionInfo composed of /proc/self/cgroup (SLURM job_id), list_running_servers (Jupyter URL/token/port/root), Jupyter HTTP /api/sessions (attached notebooks), nvidia-smi (GPU residents), and discover_other_servers for sibling Jupyters.
• /aexp-jupyter-connect and /aexp-jupyter-discover slash commands. /aexp-jupyter-iterate gains a Step 0 to confirm identity before touching cells.
• PostToolUse hook jupyter_connect_postuse fires after every connect_to_jupyter, telling the agent to re-run init() and state the populated fields back to the user before any further execute_code. Registered automatically when --with-jupyter was ever used (sticky bit honored).
• MCP tools jupyter_introspect_current + jupyter_parse_introspection use recipe-based dispatch so the aexp MCP and Jupyter MCP stay decoupled.

Also fixes a cross-platform install bug where wheels built on Windows with core.autocrlf=true shipped CRLF text files, causing aexp install to forever report skipped_conflict on every text file in any consumer repo whose on-disk copy used a different EOL convention:

• .gitattributes forces LF in the working tree for every text type we ship, so future wheels always carry LF bytes regardless of build OS.
• _files_identical does EOL-normalized comparison for known text extensions (binary files still compared strict-bytewise).
• _copy_file writes LF for text regardless of source EOL, so even a stale CRLF wheel installs LF files on disk.
• 7 new install tests cover CRLF<->LF equivalence, binary strictness, end-to-end re-install behavior, and a .gitattributes presence guard.

Pyproject bumped 0.2.1 -> 0.3.0. Full suite 428/429 (the one expected fail clears once editable installs are refreshed).