hermes - 💡(How to fix) Fix feat: User-friendly compression UI — percentage slider, absolute token selector, human-readable labels

Problem

The compression config currently uses:

• threshold: 0.50 — unintuitive for new users who use agents for the first time (is this 50%? 0.5%?)
• target_ratio: 0.20 — unclear what "ratio" refers to
• No visualization of what these values mean relative to the model's actual context window
• When switching between models with different context windows (1M vs 256K), the same ratio behaves very differently

Proposed UI

A selector panel in Dashboard/settings with two modes:

Mode 1: Percentage of context

• Slider: 0%–100%
• Display: "50% of context" instead of 0.5
• Shows computed value: "128K tokens" (auto-calculated from model's context_length)

Mode 2: Absolute token count

• Input field: "128" with unit label "K tokens"
• Presets: 64K, 128K, 256K
• Shows corresponding percentage

Human-readable labels

Instead of threshold / target_ratio:

• "Compression trigger at" / "Сжимать при достижении"
• "Compress down to" / "Сжимать до"

Context-aware

• Auto-detect model's context_length from config
• Show: "128K / 1M tokens used" live status

Use case

User switches between 1M and 256K models. With ratio-only (0.5), 128K tokens = 50% for 256K but only 12.5% for 1M. With absolute mode, set 128K once — consistent across all models.

Backward compatibility

• Backend config keys (threshold, target_ratio) unchanged
• UI writes to same keys
• If both percentage and absolute values are set, absolute takes priority

Cross-reference

Builds on the backend work in #24695 (fixed token threshold support in config). This issue focuses on the user-facing interface layer.