feat: MCP Resources — expose session data as readable resources

[OneStepAt4time]

M1.2 — MCP Resources

Parent: #440 (Roadmap)
Milestone: M1 — MCP Server Complete
Depends on: #441 (tool completeness — for AegisClient methods)

Context

MCP Resources allow agents to read data passively without tool calls. This is useful for context injection — the agent's context window can include session transcripts without explicitly calling a tool.

Resources to implement

URI	Description
aegis://sessions	List of active sessions (compact: id, name, status, workDir)
aegis://sessions/{id}/transcript	Full JSONL transcript of a session
aegis://sessions/{id}/pane	Current terminal pane content
aegis://health	Server health status

Technical approach

• Use MCP SDK server.resource() API
• Resources should support subscribe for live updates where applicable
• listChanged notification when sessions are created/killed

Acceptance criteria

• All 4 resources implemented
• resources/list returns correct URIs
• resources/read returns formatted content
• Subscribe works for session list changes