feat: custom shell prompt pattern and auto-reply (#20)

[bvisible]

Summary

Adds two new per-server configuration options to support non-standard shells (e.g., AIX with interactive login prompts):

• prompt_pattern: Custom shell prompt regex pattern (default: [$#>])
• auto_reply: Auto-respond to interactive login prompts before the shell is ready

Fixes #20

Configuration

Custom prompt pattern

TOML:

[ssh_servers.aix_server]
host = "aix.example.com"
user = "researcher"
prompt_pattern = "-->"

.env:

SSH_SERVER_AIX_PROMPT_PATTERN=-->

Auto-reply on login

TOML:

[ssh_servers.aix_server]
host = "aix.example.com"
user = "researcher"
prompt_pattern = "-->"

[[ssh_servers.aix_server.auto_reply]]
pattern = "START GLOBUS Y/N"
response = "N"
timeout = 5000

.env:

SSH_SERVER_AIX_AUTO_REPLY_COUNT=1
SSH_SERVER_AIX_AUTO_REPLY_1_PATTERN=START GLOBUS Y/N
SSH_SERVER_AIX_AUTO_REPLY_1_RESPONSE=N
SSH_SERVER_AIX_AUTO_REPLY_1_TIMEOUT=5000

Changes

• src/session-manager.js: Configurable promptPattern on SSHSession, auto-reply loop during shell initialization
• src/config-loader.js: Parse prompt_pattern and auto_reply from both TOML and .env formats
• src/index.js: Pass server config options to createSession()

Test plan

• Default behavior unchanged (no prompt_pattern → matches $, #, >)
• Custom prompt pattern --> detected correctly
• Auto-reply sends response when pattern matched during login
• Timeout works when pattern is never matched
• TOML and .env config formats both work