feat(psp-1): Major structural and terminological overhaul

This commit introduces a major refactoring of PSP-1 to improve clarity, precision, and implementer experience. The document has been restructured to separate normative statements from informative content, a consistent naming convention has been adopted, and several key concepts have been expanded and clarified.

A primary motivation is to make the specification more directly implementable by providing a clear normative kernel, explicit algorithms, and unambiguous terminology.

- **New Document Structure:**
  - Introduced a "Normative Kernel" section (4) to consolidate all core verification logic.
  - Added a new top-level "Artifacts" section (5) to provide detailed normative descriptions of `Grants`, `Presentations`, and `Delegation & Attenuation`.
  - Massively expanded the "Motivation and Rationale" section (3) with detailed design principles, a threat model, and rationale for key design choices.
  - Added a dedicated "Examples and Conformance Test Vectors" section (9).

- **Standardized Naming Convention:**
  - All specification identifiers (builtin `op` names, pin IDs, context keys, conceptual fields) have been standardized to `lower-camelCase`.
  - Examples: `grant_ref` -> `grantRef`, `builtins_id` -> `builtinsId`, `within_time` -> `withinTime`, `ctx_eq` -> `ctxEq`.
  - Added a new section `2.3 Identifier & casing convention` to make this rule explicit.

- **Enhanced Semantic Pinning (BREAKING CHANGE):**
  - **`schemesSnapshotId` Pin:** Grants **MUST** now include a `schemesSnapshotId` pin. This is a content-addressed manifest that maps resource schemes (e.g., `vault:`) to their exact comparator snapshot, preventing comparator drift. This was previously implicit and is now a required, verifiable pin.
  - The "Semantic Pinning" section (4.4) has been completely rewritten to be more normative and precise about a Grant's required pins and delegation compatibility rules.

- **Expanded Definitions:**
  - **New Terminology:** Added formal definitions for `Local Availability`, `CEP Placement Variants` (`CEP(R)`, `CEP(P)`, `CEP(S)`), and `Bridge Adapter (BA)`.
  - **Pin:** The definition of a `Pin` is now more generic and detailed, covering CIDs and URIs.

- **Improved Normative Clarity:**
  - **Verification Algorithm:** Rewritten into a more precise, step-by-step algorithm in section `4.6`.
  - **Fail-Closed Catalogue:** Added a comprehensive table (`4.8`) summarizing all conditions that **MUST** result in a denial.
  - **Time Model:** Added a dedicated section `4.7` to clarify the "single time capture" rule and the use of half-open intervals.

- **Documentation & Examples:**
  - Added section `2.4 Interpretation of JSON Projections` to clarify that JSON examples are non-normative.
  - Narrative examples in section `9.1` are now much more detailed, including illustrative Grant/Presentation projections and a CEP evaluation outline.
  - Conformance test vectors are now integrated into the main body in section `9.2`.

- **PSP Dependencies:**
  - `PSP-4` is now listed as a formal dependency.
  - `PSP-2` is now listed as an "Informative reference" rather than a hard dependency for the core model.

- **Minor Changes:**
  - Added a "Backwards Compatibility" section (7).
  - Merged old "Overview and Goals" into the new "Motivation and Rationale" section.
  - The CDDL grammar and builtin operator tables have been updated to reflect the new `camelCase` naming.
  - Removed "Appendix D - Suggested Reason Codes" in favor of the fail-closed catalogue.

BREAKING CHANGE: This commit introduces significant breaking changes.
1.  **Naming Convention:** All identifiers are now `lower-camelCase`. Implementations must update field names, builtin operator calls, and pin lookups.
2.  **Required `schemesSnapshotId` Pin:** All Grants must now include the `schemesSnapshotId` pin. Verification logic must be updated to check for its presence and enforce compatibility across delegation chains.

Author: CMCDragonkai