feat(gastown): custom per-role prompt instructions in town settings

[jrf0110]

Summary

• Add custom_instructions field to town config schema, allowing users to append free-text instructions (up to 2000 chars each) to the system prompt for polecat, refinery, and mayor agents
• Add "Custom Instructions" section to town settings UI with per-role textareas, character counters, and scrollspy nav entry
• Instructions are appended as a ## Custom Instructions (from town settings) section at the end of each role's system prompt via appendCustomInstructions() in the dispatch path
• For the mayor (whose prompt lives in AGENTS.md on disk), a new PUT /agents/:agentId/system-prompt container endpoint rewrites AGENTS.md when instructions change, triggered automatically from the updateTownConfig mutation
• Widens all gastown drawers by ~120px and removes truncate from drawer title headers for better readability

Closes #1794

Verification

• pnpm typecheck passes (only pre-existing csv-parse/sync error in a migration script)
• oxfmt --list-different . passes (no formatting issues)
• Regenerated gastown tRPC type declarations via pnpm build:types

Visual Changes

Reviewer Notes

• The appendCustomInstructions helper in container-dispatch.ts is applied at the single point where systemPrompt is assembled in startAgentInContainer, covering all roles (polecat uses systemPromptForRole, refinery uses systemPromptOverride, mayor uses systemPromptForRole — all get wrapped)
• Mayor propagation requires special handling because its prompt is written to AGENTS.md (read by kilo serve) rather than passed via the session API. The new updateMayorSystemPrompt() method on TownDO rebuilds the prompt and pushes it to the container when custom_instructions.mayor changes
• Empty/null instructions inject nothing (no empty section header)
• The custom_instructions field is fully optional and backward-compatible — existing towns without it behave identically

[kilo-code-bot]

Code Review Summary

Status: 3 Issues Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	3
SUGGESTION	0

Issue Details (click to expand)

WARNING

File	Line	Issue
cloudflare-gastown/scripts/test-drain.sh	63	Container lookup grabs the first towncontainerdo container, so the script can monitor the wrong town when multiple containers are running.
cloudflare-gastown/scripts/test-drain.sh	123	`grep -c ...
cloudflare-gastown/docs/local-debug-testing.md	272	docker kill $(docker ps -q) kills every running Docker container instead of only the Gastown/Wrangler containers.

Fix these issues in Kilo Cloud

Other Observations (not in diff)

N/A

Files Reviewed (2 files)

• cloudflare-gastown/docs/local-debug-testing.md - 1 issue
• cloudflare-gastown/scripts/test-drain.sh - 2 issues

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_{Reviewed by gpt-5.4-20260305 · 171,643 tokens}

[jeanduplessis]

Due to the monorepo restructure you will need to recreate this PR on a new branch from main. Pass the prompt found at, https://github.com/Kilo-Org/cloud/blob/main/plans/monorepo-migration-prompt.md, to your coding agent while running in this branch. Please close this PR once done or if you don't plan to proceed with it.

[jrf0110]

Rebased onto gastown-staging with the monorepo restructure applied. All file paths updated from cloudflare-gastown/ → services/gastown/ and src/ → apps/web/src/. The docs and test-drain script were already on gastown-staging so they're excluded from this PR's diff now. Target branch changed to gastown-staging.