agents: reduce prompt token bloat from exec and context (#16539)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 8e1635fa3f
Co-authored-by: CharlieGreenman <8540141+CharlieGreenman@users.noreply.github.com>
Co-authored-by: gumadeiras <5599352+gumadeiras@users.noreply.github.com>
Reviewed-by: @gumadeiras

src/config/schema.help.ts

@@ -64,6 +64,8 @@ export const FIELD_HELP: Record<string, string> = {
     'Optional allowlist of model ids (e.g. "gpt-5.2" or "openai/gpt-5.2").',
   "tools.exec.notifyOnExit":
     "When true (default), backgrounded exec sessions enqueue a system event and request a heartbeat on exit.",
+  "tools.exec.notifyOnExitEmptySuccess":
+    "When true, successful backgrounded exec exits with empty output still enqueue a completion system event (default: false).",
   "tools.exec.pathPrepend": "Directories to prepend to PATH for exec runs (gateway/sandbox).",
   "tools.exec.safeBins":
     "Allow stdin-only safe binaries to run without explicit allowlist entries.",
@@ -140,6 +142,8 @@ export const FIELD_HELP: Record<string, string> = {
   "auth.cooldowns.failureWindowHours": "Failure window (hours) for backoff counters (default: 24).",
   "agents.defaults.bootstrapMaxChars":
     "Max characters of each workspace bootstrap file injected into the system prompt before truncation (default: 20000).",
+  "agents.defaults.bootstrapTotalMaxChars":
+    "Max total characters across all injected workspace bootstrap files (default: 24000).",
   "agents.defaults.repoRoot":
     "Optional repository root shown in the system prompt runtime line (overrides auto-detect).",
   "agents.defaults.envelopeTimezone":