claw-api: warn on principal verb skew and surface inert principals

[mostlydev]

This pull request enhances principal management and diagnostics in the Claw API by improving health endpoint reporting, adding principal normalization and version skew warnings, and expanding test coverage. It introduces mechanisms to warn users when a configured principal requires API features that may not be supported by the deployed Claw API version, and surfaces principal-related diagnostics via the /health endpoint.

Health endpoint improvements:

• The /health endpoint now returns detailed principal diagnostics, including the total principal count, a list of inert principals (those with no recognized verbs), and any normalization warnings about principal configuration.
• The handler test suite is updated to validate the new health endpoint response and to check for inclusion of normalization warnings and inert principal reporting.

Principal store and normalization enhancements:

• The Store struct now retains normalization warnings, and exposes an InertPrincipalNames method to summarize inert principals. [1] [2]
• Tests are added to ensure normalization warnings are retained and inert principal summaries are accurate. [1] [2]

Principal version skew detection:

• Adds PrincipalVersionSkewWarnings, which emits warnings if principals require verbs not supported by the specified Claw API image version. This helps prevent misconfiguration when using older API images.
• The Claw API runtime preparation now prints these warnings to stdout if version mismatches are detected.
• Comprehensive tests are included to verify warning emission for version mismatches, supported versions, and unpinned images. [1] [2]

Dependency update:

• Imports golang.org/x/mod/semver to support semantic version comparison for image tag checking.