Add tiger mcp get command

[nathanjcochran]

This PR adds a new tiger mcp get <type> <name> command that allows users to inspect detailed information about specific MCP capabilities (tools, prompts, resources, and resource templates).

New Command

The tiger mcp get command provides detailed, human-readable information about MCP capabilities:

# Get details about a tool
tiger mcp get tool service_create

# Get details about a prompt
tiger mcp get prompt setup-timescaledb-hypertables

# Output as JSON or YAML
tiger mcp get tool service_create -o json
tiger mcp get tool service_create -o yaml

It is also aliased as tiger mcp show and tiger mcp describe (to match the tiger service get aliases).

Note that I first tried outputting the information in a table (when not requesting JSON/YAML formatted output), but I found it too difficult to read due to the amount of text in the tool descriptions and input/output schemas. I therefore decided use a raw text format roughly similar to how Claude Code displays tools when you inspect one via /mcp (though there are some differences, such as the fact that I show the output schema as well as the input schema). I'm open to other thoughts and feedback on this though.

Additional Changes

• Explicit tool annotations: Made annotation hints explicit (ReadOnlyHint, IdempotentHint, OpenWorldHint) instead of relying on default values, improving code clarity and ensuring that they're displayed correctly in the tiger mcp get output.
• Shell completion helper: Added filterCompletionsByPrefix helper function to consolidate completion filtering logic
• Tests: Added tests for the new tiger mcp get command.

Closes AGE-287