refactor(daemon): remove context snapshot, let agent fetch data via CLI

Replace the frozen context snapshot pattern with a CLI-driven approach:
agents now use `multica` CLI commands to fetch issue details, comments,
and workspace context on demand, always getting the latest data.

- Remove buildContextSnapshot and snapshot generation from enqueue
- Claim endpoint now returns fresh agent name + skills from DB
- Daemon resolves provider from local runtimeIndex, not snapshot
- Prompt instructs agent to use `multica issue get` / `comment list`
- Meta skill (CLAUDE.md/AGENTS.md) documents all available CLI commands
- Skills still injected as filesystem files (static agent config)
- Simplify daemon types: remove TaskContext/IssueContext/RuntimeContext

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/internal/daemon/execenv/execenv.go

@@ -29,11 +29,9 @@ type PrepareParams struct {
 
 // TaskContextForEnv is the subset of task context used for writing context files.
 type TaskContextForEnv struct {
-	IssueTitle       string
-	IssueDescription string
-	WorkspaceContext string
-	AgentName          string
-	AgentSkills        []SkillContextForEnv
+	IssueID     string
+	AgentName   string
+	AgentSkills []SkillContextForEnv
 }
 
 // SkillContextForEnv represents a skill to be written into the execution environment.