fix: remove duplicate system prompt in CleanContextRunner

[withRiver]

The CleanContextRunner was passing the system prompt via two paths simultaneously:

1. config.agents.defaults.systemPromptOverride (primary)
2. extraSystemPrompt parameter (legacy fallback)

On openclaw >= 2026.4.7, both paths are active, causing the same prompt to appear twice in the final system message, wasting tokens per LLM call.

Remove the extraSystemPrompt parameter since systemPromptOverride fully handles the system prompt injection. This fixes the duplication for all downstream consumers: L1 extraction, L1 dedup, L2 scene extraction, and L3 persona generation.

Problem

CleanContextRunner passes the system prompt to runEmbeddedPiAgent via two paths simultaneously:

1. config.agents.defaults.systemPromptOverride — the primary path, which completely replaces the default agent system prompt
2. extraSystemPrompt parameter — a legacy fallback intended for older versions of openclaw

On current versions of openclaw, both paths are active. In openclaw/src/agents/pi-embedded-runner/run/attempt-system-prompt.ts, buildAttemptSystemPrompt processes them as follows:

// openclaw/src/agents/pi-embedded-runner/run/attempt-system-prompt.ts
const baseSystemPrompt = params.systemPromptOverrideText
  ? appendModelIdentitySystemPrompt({
      systemPrompt: appendRuntimeExtraSystemPrompt({
        systemPrompt: params.systemPromptOverrideText,              // ← path A: override
        extraSystemPrompt: params.embeddedSystemPrompt.extraSystemPrompt,  // ← path B: appended!
        ...
      }),
      ...
    })
  : buildEmbeddedSystemPrompt(...);

When systemPromptOverrideText is present, appendRuntimeExtraSystemPrompt appends extraSystemPrompt after it. Since both contain the same content (e.g. EXTRACT_MEMORIES_SYSTEM_PROMPT), the final system message becomes:

{EXTRACT_MEMORIES_SYSTEM_PROMPT}          ← from systemPromptOverride

## Group Chat Context
{EXTRACT_MEMORIES_SYSTEM_PROMPT}          ← from extraSystemPrompt (duplicate!)

{model identity line}

This affects all modules that use CleanContextRunner:

• L1 memory extraction (l1-extractor.ts)
• L1 conflict detection / dedup (l1-dedup.ts)
• L2 scene extraction (scene-extractor.ts)
• L3 persona generation (persona-generator.ts)

Impact

• Extra tokens wasted per LLM call (the full system prompt is sent twice)
• Larger lantency

Fix

Remove the extraSystemPrompt parameter from the runEmbeddedPiAgent call in CleanContextRunner.run(). The system prompt is already fully handled via config.agents.defaults.systemPromptOverride.

After this fix, on openclaw < 2026.4.7, users should enable the LLM configuration item for the plugin, so as to use the StandaloneLLMRunner instead of CleanContextRunner.

Changes

• src/utils/clean-context-runner.ts: Remove effectiveSystemPrompt variable and extraSystemPrompt parameter passed to runEmbeddedPiAgent

[YOMXXX]

Reviewer triage notes:

CI blocker:

• Size Guard is failing: the package tarball is 631 KB, above the current 512 KB limit. The likely fix is to apply the same package file-list cleanup used in feat(capture): make timestamps timezone configurable #76/feat(recall): cap injected memory context #71 (stop shipping index.ts and src/ in the npm tarball), or rebase after that package fix lands.

Compatibility blocker / decision needed:

• This removes extraSystemPrompt unconditionally. The PR text says extraSystemPrompt is still needed for OpenClaw < 2026.4.7, while the package currently declares openclaw >=2026.3.7. If that older range is still supported, this is a behavior regression for 2026.3.x/early 2026.4.x users.

Suggested resolution: either bump the declared minimum OpenClaw version to the version where systemPromptOverride is guaranteed, or keep a version/capability-gated fallback path for older OpenClaw. Once that decision and Size Guard are handled, the code change itself is small and easy to review.

[YOMXXX]

I opened #86 as a compatibility-preserving alternative to this PR. It keeps extraSystemPrompt for unknown / older OpenClaw versions, omits it for 2026.4.7+, adds unit coverage for the version gate, and CI is green including Size Guard. Reviewers can compare #86 if they want to avoid changing the declared OpenClaw compatibility range.