refactor(core): move shell tool config into state

[nexxeln]

summary

• expose effective truncation limits from ToolOutput
• project portable scanner config into reloadable ShellPolicy state
• remove direct Config reads from ShellTool while preserving live reload behavior

testing

• bun typecheck from packages/core
• bun test test/config/shell.test.ts test/config/tool-output.test.ts
• bun test test/tool-shell.test.ts
• bun test test/location-layer.test.ts
• bun test test/workerd.test.ts from packages/server
• focused config and shell policy tests with --rerun-each 5
• pre-push monorepo typecheck