feat(marketplace): implement plugin marketplace

Implements a new plugin marketplace structure and expands repository
support beyond basic skills to include plugins, MCPs, hooks, etc.

dist/agy/date-time/plugin.json

@@ -0,0 +1,4 @@
+{
+  "name": "date-time",
+  "description": "Retrieves the exact current date and time for time-sensitive queries, scheduling, duration calculations, and validating chronological context."
+}

dist/agy/date-time/skills/date-time/SKILL.md

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+---
+name: date-time
+description: Retrieves the exact current date and time for time-sensitive queries, scheduling, duration calculations, and validating chronological context.
+version: 1.0.0
+user-invocable: true
+author: Rootiest
+---
+
+# Current Date and Time Retrieval
+
+## Purpose
+Enables the assistant to retrieve the exact, real-time current date and time when addressing time-sensitive queries, scheduling tasks, calculating durations, or validating chronological context.
+
+## Trigger Conditions
+Activate this skill whenever the user's prompt:
+* Explicitly asks for the current date, day, time, or year.
+* References relative time expressions (e.g., "today", "yesterday", "next week", "recently").
+* Requires checking if an event has already occurred or is upcoming relative to the present moment.
+* Needs to calculate an age, duration, or countdown from the present day.
+
+## Tool Definition
+
+### `get_current_datetime`
+* **Description**: Executes the system `date` command to fetch the current local timestamp, timezone, and calendar date.
+* **Parameters**: None required.
+
+## Execution Workflow
+1. **Detect**: Recognize a time-sensitive trigger in the user's input.
+2. **Call**: Invoke the `get_current_datetime` tool before generating the final response.
+3. **Process**: Use the returned timestamp to anchor your temporal reasoning.
+4. **Respond**: Deliver an accurate answer reflecting the retrieved date/time naturally, without explicitly explaining that a tool was used unless asked.
+
+## Examples
+
+### Example 1
+* **User**: "What day of the week is it today?"
+* **Assistant Action**: Invoke `get_current_datetime`.
+* **Response**: "Today is [Day of Week], [Date]."
+
+### Example 2
+* **User**: "Is the 2026 World Cup happening this month?"
+* **Assistant Action**: Invoke `get_current_datetime`.
+* **Response**: Evaluates current month/year against the tournament schedule to provide an accurate "yes/no" or countdown.