Adopt Go-style module version selection

[itsfuad]

Goal

Adopt deterministic Go-style Minimal Version Selection and semantic import versioning.

Current boundary

Current resolver supports a narrow stable-semver constraint set for exact versions, comparisons, tilde, caret, latest, and wildcard requests. Recursive installation selects compatible versions but does not implement graph-wide MVS or semantic import versioning.

Required design

• Define module identity and major-version import-path rules.
• Replace recursive best-match resolution with deterministic graph-wide MVS.
• Specify upgrade, downgrade, exclusion, and retraction behavior.
• Preserve lockfile determinism, offline behavior, integrity checks, and mock registry support.
• Define manifest and lockfile migration before removing tactical constraint semantics.
• Add compatibility, conflict, diamond-dependency, replacement, and repeatability fixtures before migration.

Constraints

• Do not extend current compatibility resolver piecemeal.
• Design canonical graph algorithm and import-version model first.
• One resolved module version must serve whole build graph unless semantic import versioning gives major versions distinct identities.
• Diagnostics must explain selected version and forcing dependency path.

Relationships

• Independent from language-foundation milestone.
• Auto-import tooling in Add auto-import operation completion #74 must consume canonical resolved module identities after this model lands; Add auto-import operation completion #74 must not invent a second resolver.

Validation

• Resolver unit tests for MVS, upgrades, downgrades, exclusions, retractions, and major-version paths.
• End-to-end local and mock-registry fixtures.
• Stable lockfile output across dependency traversal order.
• Offline and integrity-failure diagnostics.