fix(instances): decode percent-encoded route names

[vernonstinebaker]

Summary

• decode percent-encoded component and instance path segments before instance route dispatch
• update config, logs, update, channels, cron, history, skills, integration, and agent-session routes to use owned decoded values
• add regression coverage for spaced and special-character instance names across parser, server, and managed instance flows

Testing

• zig build test -Dembed-ui=false -Dbuild-ui=false --summary all
• zig build

Scope

• excludes the imported-standalone follow-up bugs found during manual testing; those are tracked separately and not included in this PR