refactor(domain): store operation mode as typed enum

[stritti]

Summary

Adopts the typed OperationMode contract from #214 inside OperationModeNode while preserving all existing String-facing APIs and external values.

Changes

• store _mode as OperationMode instead of Arduino String
• add typed setMode(OperationMode, source) and getTypedMode()
• keep setMode(String) / getMode() / getModeCStr() as compatibility boundaries
• parse persisted/string values through the allocation-free contract helper
• compare rules against the stable external representation
• persist the unchanged wire/NVS values (auto, manu, boost, timer)

Why

This removes protocol strings from the mutable domain state without forcing MQTT/Web/UI call sites to migrate in the same PR. It is the next small step toward typed commands and a pure application runtime.

Compatibility

No MQTT, Web or NVS value changes. The historic manu representation remains unchanged.

Stacked on #214.

[github-actions]

✅⚠️MegaLinter analysis: Success with warnings

Descriptor	Linter	Files	Fixed	Errors	Max errors	Warnings	Elapsed time
✅ ACTION	actionlint	8		0		0	0.78s
✅ BASH	bash-exec	2		0		0	0.64s
✅ BASH	shellcheck	2		0		0	0.7s
✅ BASH	shfmt	2		0		0	0.01s
✅ C	clang-format	1		0		0	0.04s
✅ C	cppcheck	1		0		0	0.04s
✅ C	cpplint	1		0		0	0.33s
✅ CPP	clang-format	90		0		0	0.78s
✅ CPP	cppcheck	90		0		0	7.04s
✅ CPP	cpplint	90		0		0	8.5s
✅ EDITORCONFIG	editorconfig-checker	275		0		0	0.48s
✅ JSON	jsonlint	6		0		0	0.13s
✅ JSON	v8r	6		0		0	4.05s
⚠️ MARKDOWN	markdownlint	107		4		0	5.19s
✅ YAML	yamllint	26		0		0	0.96s

Detailed Issues

⚠️ MARKDOWN / markdownlint - 4 errors

.opencode/skills/web-ui/SKILL.md:34 error MD028/no-blanks-blockquote Blank line inside blockquote
docs/superpowers/plans/2026-08-10-olimex-c6-local-ui-implementation.md:106:401 error MD013/line-length Line length [Expected: 400; Actual: 452]
docs/superpowers/plans/2026-08-16-norvi-button-calibration.md:7:401 error MD013/line-length Line length [Expected: 400; Actual: 412]
openspec/changes/controller-architecture-contracts/design.md:171:401 error MD013/line-length Line length [Expected: 400; Actual: 448]

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Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

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Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

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Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

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[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

[chatgpt-codex-connector]

You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	48.2%
Branch Coverage	74.8%
Lines Hit/Total	392/814
Branches Hit/Total	178/238

Report from native unit tests (ASan + gcov).

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You have reached your Codex usage limits for code reviews. You can see your limits in the Codex usage dashboard.

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Native Test Coverage

Metric	Value
Line Coverage	49.3%
Branch Coverage	76.4%
Lines Hit/Total	411/833
Branches Hit/Total	194/254

Report from native unit tests (ASan + gcov).