Migrate PRD to OpenSpec format

documentation/architecture/openspec/specs/falsifier/spec.md

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+# Falsifier
+
+## Purpose
+The library provides a minimal, focused foundation for creating falsey objects in Python that maintain distinct identities. It serves developers who need sentinel values, absence indicators, or custom falsey types where `None` or `False` may be semantically meaningful values.
+
+## Requirements
+
+### Requirement: Boolean Evaluation
+The `Falsifier` class SHALL implement `__bool__` to return `False`.
+
+Priority: Critical
+
+#### Scenario: Boolean context
+- **WHEN** a `Falsifier` instance is used in a boolean context
+- **THEN** it evaluates to `False`
+
+### Requirement: Identity-Based Hashing
+The `Falsifier` class SHALL implement `__hash__` using object identity (`id(self)`).
+
+Priority: High
+
+#### Scenario: Hashing
+- **WHEN** `hash()` is called on a `Falsifier` instance
+- **THEN** it returns the integer identity of the object
+
+### Requirement: String Representations
+The `Falsifier` class SHALL provide distinct string representations.
+
+Priority: Medium
+
+#### Scenario: String conversion
+- **WHEN** `str()` is called on a `Falsifier` instance
+- **THEN** it returns `'False_'`
+
+#### Scenario: Representation
+- **WHEN** `repr()` is called on a `Falsifier` instance
+- **THEN** it returns the fully qualified class name with empty call syntax
+
+### Requirement: Equality Comparison
+The `Falsifier` class SHALL implement identity-based equality comparison.
+
+Priority: Critical
+
+#### Scenario: Identity equality
+- **WHEN** a `Falsifier` instance is compared to itself using `==`
+- **THEN** it returns `True`
+
+#### Scenario: Distinct object inequality
+- **WHEN** a `Falsifier` instance is compared to a different instance using `==`
+- **THEN** it returns `False`
+
+#### Scenario: Inequality operator
+- **WHEN** a `Falsifier` instance is compared to a different instance using `!=`
+- **THEN** it returns `True`
+
+### Requirement: Ordered Comparison Rejection
+The `Falsifier` class SHALL implement `__lt__`, `__le__`, `__gt__`, and `__ge__` to return `NotImplemented`.
+
+Priority: Low
+
+#### Scenario: Less than comparison
+- **WHEN** a `Falsifier` instance is compared using `<`
+- **THEN** it raises `TypeError` (assuming other operand returns `NotImplemented`)
+
+### Requirement: Subclass Compatibility
+The `Falsifier` class SHALL support subclassing without requiring special metaclass machinery.
+
+Priority: Medium
+
+#### Scenario: Creating a subclass
+- **WHEN** a class inherits from `Falsifier`
+- **THEN** instances of the subclass evaluate to `False`
+- **AND** instances of the subclass maintain distinct identity