feat(api): compress old tool_result content for small-context providers (#801)

* feat(api): compress old tool_result content for small-context providers

Adds a shim-layer pass that tiers tool_result content by age on
providers
  with small effective context windows (Copilot gpt-4o 128k, Mistral,
  Ollama). Recent turns remain full; mid-tier results are truncated to
2k
  chars; older results are replaced with a stub that preserves tool name
  and arguments so the model can re-invoke if needed.

  Tier sizes auto-tune via getEffectiveContextWindowSize, same
calculation
  used by auto-compact. Reuses COMPACTABLE_TOOLS and
  TOOL_RESULT_CLEARED_MESSAGE to complement (not duplicate)
microCompact.
  Configurable via /config toolHistoryCompressionEnabled.

  Addresses active-session context accumulation on Copilot where
  microCompact's time-based trigger never fires, which surfaces as
  "tools appearing in a loop" and prompt_too_long errors after ~15
turns.

* fix: config tool history

src/utils/config.ts

@@ -244,6 +244,7 @@ export type GlobalConfig = {
   bypassPermissionsModeAccepted?: boolean
   hasUsedBackslashReturn?: boolean
   autoCompactEnabled: boolean // Controls whether auto-compact is enabled
+  toolHistoryCompressionEnabled: boolean // Compress old tool_result content for small-context providers
   showTurnDuration: boolean // Controls whether to show turn duration message (e.g., "Cooked for 1m 6s")
   /**
    * @deprecated Use settings.env instead.
@@ -622,6 +623,7 @@ function createDefaultGlobalConfig(): GlobalConfig {
     verbose: false,
     editorMode: 'normal',
     autoCompactEnabled: true,
+    toolHistoryCompressionEnabled: true,
     showTurnDuration: true,
     hasSeenTasksHint: false,
     hasUsedStash: false,
@@ -668,6 +670,7 @@ export const GLOBAL_CONFIG_KEYS = [
   'editorMode',
   'hasUsedBackslashReturn',
   'autoCompactEnabled',
+  'toolHistoryCompressionEnabled',
   'showTurnDuration',
   'diffTool',
   'env',