Add implicit project-scope detection and doctor health checks

[polymorcodeus]

Summary

Adds implicit project-scope integration for lnk update, lnk restore, and lnk doctor. When a command runs inside a git repo that contains a .lnkinclude file, the project scope is detected automatically and restored alongside the common and host scopes. lnk doctor now audits project storage, symlinks, and patterns.

What's new

• Implicit project detection - DetectProjectScope resolves the project root, ID, and storage resolver from the current working directory when a .lnkinclude file is present.
• Update/restore integration - RestoreWithProject and UpdateWithProject restore common, host, and detected project scope, logging (project scope: <id>) to stderr.
• --no-project opt-out - global flag skips automatic project-scope detection for both update and restore.
• Doctor project checks - lnk doctor reports orphaned project storage, broken project symlinks, and .lnkinclude patterns that match no files.
• Issue formatting - project health issues print with severity, project ID, issue, and a suggested fix.

Usage

Command	Purpose
lnk update	Pull repo changes and restore common, host, and detected project scope
lnk restore	Restore common, host, and detected project scope
lnk update --no-project / lnk restore --no-project	Skip automatic project-scope detection
lnk doctor	Audit project storage, symlinks, and patterns

Behavior changes / guardrails

• The lnk repository itself is never treated as a project, even if it contains a .lnkinclude file.
• Project detection works from any subdirectory of the project git repo.
• --no-project is a persistent global flag, so it is available on any subcommand.
• Orphaned storage detection walks $HOME looking for .lnkinclude files and compares live project IDs against stored project IDs.
• Broken symlink detection only reports symlinks that point into the project's lnk storage and whose target is missing.
• Empty-pattern detection skips negation patterns and checks each positive pattern against files in the project directory.

Testing

• Unit tests for DetectProjectScope, RestoreWithProject, and UpdateWithProject.
• Unit tests for orphaned storage, broken symlinks, empty patterns, and a healthy-project baseline in lnk doctor.
• make check runs fmt, vet, lint, unit, and integration suites; all green.