refactor(application): add coherent controller snapshot store

[stritti]

Summary

Adds the synchronized read-model store needed to move MQTT, Web and display code away from direct reads of global mutable nodes.

Changes

• add ControllerSnapshotStore
• publish/read complete SystemSnapshot values under a short critical section
• ESP32 uses portMUX; native tests use std::mutex
• adapters receive copies, never references into mutable controller state
• add tests for empty state, complete-copy semantics and whole-snapshot replacement
• update the architecture OpenSpec task list

Why

#170 establishes a single-writer ownership boundary for mutable controller state. This store gives outbound adapters the matching read boundary: one coherent value object instead of individually synchronized fields or direct Nodes.hpp access.

Scope

This PR does not yet migrate MQTT/Web/display call sites. That migration can be done independently once the store exists and the Core-1 runtime publishes the projection.

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	0.53s
✅ BASH	bash-exec	2		0		0	0.43s
✅ BASH	shellcheck	2		0		0	0.46s
✅ BASH	shfmt	2		0		0	0.01s
✅ C	clang-format	1		0		0	0.04s
✅ C	cppcheck	1		0		0	0.02s
✅ C	cpplint	1		0		0	0.29s
✅ CPP	clang-format	94		0		0	0.63s
✅ CPP	cppcheck	94		0		0	5.25s
✅ CPP	cpplint	94		0		0	6.11s
✅ EDITORCONFIG	editorconfig-checker	279		0		0	0.55s
✅ JSON	jsonlint	6		0		0	0.15s
✅ JSON	v8r	6		0		0	3.8s
⚠️ MARKDOWN	markdownlint	107		4		0	3.71s
✅ YAML	yamllint	26		0		0	0.75s

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	49.5%
Branch Coverage	75.0%
Lines Hit/Total	413/835
Branches Hit/Total	180/240

Report from native unit tests (ASan + gcov).

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Native Test Coverage

Metric	Value
Line Coverage	49.5%
Branch Coverage	75.0%
Lines Hit/Total	413/835
Branches Hit/Total	180/240

Report from native unit tests (ASan + gcov).

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[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	49.5%
Branch Coverage	75.0%
Lines Hit/Total	413/835
Branches Hit/Total	180/240

Report from native unit tests (ASan + gcov).

[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	49.5%
Branch Coverage	75.0%
Lines Hit/Total	413/835
Branches Hit/Total	180/240

Report from native unit tests (ASan + gcov).

[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	49.5%
Branch Coverage	75.0%
Lines Hit/Total	413/835
Branches Hit/Total	180/240

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	50.6%
Branch Coverage	76.6%
Lines Hit/Total	432/854
Branches Hit/Total	196/256

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.

[github-actions]

Native Test Coverage

Metric	Value
Line Coverage	50.6%
Branch Coverage	76.6%
Lines Hit/Total	432/854
Branches Hit/Total	196/256

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	52.0%
Branch Coverage	76.9%
Lines Hit/Total	458/880
Branches Hit/Total	200/260

Report from native unit tests (ASan + gcov).