fix(devcontainer): use Pylon’s current setup workflow

[rynfar]

The old devcontainer installs with Bun despite Pylon's current Vite+/pnpm workflow. Replace it with Ubuntu 24.04, Node 24, Rust, GitHub CLI, and lifecycle scripts that install dependencies, repair Electron permissions, and warm the web cache.

Adapts pingdotgg/t3code#7875 (7376536b23e8db0d1b09054bbc0b919cf0c85405). Keep Pylon names and independent cache volumes, its 0.2.2 Vite+ pin and current contributor guide. Persist the pinned CLI’s VP_HOME directory across lifecycle shells, explicitly place pnpm's store in the cache volume, document actual forwarded ports, and keep state in the workspace .t3.

Both lifecycle scripts pass shell syntax checks; scoped formatting and git diff --check pass. The Dev Container CLI successfully created an Ubuntu/Node 24 container from an independent disposable checkout, installed all dependencies with pnpm 11.10.0, repaired Electron, and warmed the web cache. Recreating the container reused the mounted caches and completed the full lifecycle again; the second dependency install took 1.3 seconds. This real check caught and fixed the pinned Vite+ 0.2.2 single-root installer path and cache ownership before its installer runs. No runtime application behavior changed.

Model: GPT-6 Astra. Harness: Codex.

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.7 KiB	13.8 KiB	+164 B (+1.2%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.1 KiB	7.1 KiB	0 B (0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.6 KiB	6.7 KiB	+164 B (+2.4%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	56.5 KiB	57.4 KiB	+910 B (+1.6%)	66.4 KiB	✅
Codex	Live turn messages	8	10	+2 (+25.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.8 KiB	+211 B (+1.5%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.1 KiB	7.1 KiB	−3 B (−0.0%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.7 KiB	+214 B (+3.2%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.3 KiB	58.2 KiB	+972 B (+1.7%)	66.4 KiB	✅
Claude	Live turn messages	7	10	+3 (+42.9%)	21	✅

Baseline: 983633a · PR result: d5bee57 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 111.2 KiB
• Claude decoded thread snapshot: 111.9 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.