feat: cmd/low_spool MQTT handler

[sjordan0228]

Summary

• New cmd/low_spool MQTT command — middleware/HA sends true/false to start/stop LED breathing mid-print
• Uses LED's current target color (persists after tag removal) so breathing matches the last scanned spool
• LEDManager::getTargetColor() getter for reading current LED target RGB
• Fix misleading log: "Spool X synced" instead of "Spool X, 0.0g remaining" when weight not sent

Test plan

• Build succeeds
• Scan red tag, remove, send cmd/low_spool true → breathes red
• Send cmd/low_spool false → solid red
• Web log shows "Low spool: breathing enabled/disabled"

Completes #137 (gap #3 — cmd/low_spool handler)

Summary by CodeRabbit

• New Features

  • Added new MQTT command support for controlling LED indicator behavior based on spool status, enabling LED breathing effects or static display modes

• Improvements

  • Enhanced logging messages for spool weight synchronization to provide clearer feedback during updates

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

The PR adds MQTT command handling for low_spool in HomeAssistantManager that controls LED behavior by fetching the current target color and toggling between LED breathing and static display, complemented by a new LEDManager accessor method and improved weight logging in SpoolmanManager.

Changes

Cohort / File(s)	Summary
LEDManager Accessor src/LEDManager.h, src/LEDManager.cpp	Added public const method getTargetColor() to expose the internal _target RGB color components via output references.
MQTT Command Handler src/HomeAssistantManager.cpp	Implemented low_spool command that fetches target LED color, applies dim-white fallback for zero RGB values, and conditionally starts LED breathing or sets static color based on payload boolean interpretation.
Weight Logging src/SpoolmanManager.cpp	Modified updateSpool() to conditionally log remaining weight only when greater than zero; logs sync completion without numeric value otherwise.

Sequence Diagram

sequenceDiagram
    participant MQTT as MQTT Broker
    participant HAM as HomeAssistantManager
    participant LED as LEDManager
    participant Log as Logger

    MQTT->>HAM: low_spool command<br/>(payload: "true"/"false")
    HAM->>LED: getTargetColor(r, g, b)
    LED-->>HAM: return RGB values
    alt RGB all zero
        HAM->>HAM: apply dim-white fallback<br/>(r=200, g=200, b=200)
    end
    alt payload == "true"
        HAM->>LED: breatheFilamentColor()
        HAM->>Log: log "Low spool enabled"
    else payload != "true"
        HAM->>LED: showFilamentColor(r, g, b)
        HAM->>Log: log "Low spool disabled"
    end
    HAM->>MQTT: publish command response<br/>(success)

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Estimated Code Review Effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly Related Issues

• enhancement: low spool LED breathing — configurable threshold + missing paths #137: Directly implements the low_spool MQTT command handler using LEDManager's color accessor and LED control methods to address the missing feature.
• Bug: Low spool LED breathing not working — MQTT publish removed during refactor spoolsense_middleware#61: Addresses the missing spoolsense/.../cmd/low_spool handler implementation for scanner-side LED breathing control.

Possibly Related PRs

• Add set_color MQTT command handler for LED #37: Adds similar MQTT command handler in HomeAssistantManager::handleCommand that invokes LEDManager APIs (showFilamentColor), modifying the same function with parallel structure.
• feat: store and apply filament usage deductions (#123) #124: Introduces another MQTT command branch (deduct) in HomeAssistantManager::handleCommand, following the same handler pattern and file modification.

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The pull request title 'feat: cmd/low_spool MQTT handler' accurately and concisely describes the main change — adding a new MQTT command handler for low spool detection.
Description check	✅ Passed	The description includes Summary and Test plan sections matching template requirements, with specific test cases and build verification. However, it lacks the 'Changes' and 'How to Test' structural sections and missing explicit checklist items.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/cmd-low-spool

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