feat(cloud-agent): add Gastown platform filter to sessions UI

[jrf0110]

Summary

Add 'gastown' as a filterable platform option in the cloud sessions sidebar (web and mobile), so Gastown sessions are correctly tagged and filterable in the cloud sessions UI. Also removes a stale comment in CloudSidebarLayout's platform switch and adds a clarifying comment on the default branch that now handles gastown pass-through.

Verification

Manually verified that the platform filter list and label mapping are consistent across web ChatSidebar and mobile platform-filter-modal.

Visual Changes

N/A — filter chip addition matches existing pattern.

Reviewer Notes

The default case in CloudSidebarLayout.tsx already passes unknown platform strings through unchanged, which correctly handles 'gastown' without special-casing. The KILO_PLATFORM: 'gastown' value is set by the gastown process manager (confirmed by existing tests). Minor: line 59 of CloudSidebarLayout.tsx has a stray blank line from the removed comment.

[kilo-code-bot]

Code Review Summary

Status: No Issues Found | Recommendation: Merge

Executive Summary

This PR cleanly adds 'gastown' as a filterable platform option to both web and mobile session sidebars, with no logic bugs, security concerns, or behavioral regressions.

Files Reviewed (4 files)

• apps/mobile/src/components/agents/platform-filter-modal.tsx
• apps/web/src/components/cloud-agent-next/ChatSidebar.tsx
• apps/web/src/components/cloud-agent-next/CloudSidebarLayout.tsx
• services/gastown/container/src/process-manager.test.ts

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_{Reviewed by claude-sonnet-4.6 · 304,386 tokens}

_{Review guidance: REVIEW.md from base branch gastown-staging}