feat: building block run logs, definitions and versions (experimental)

[JohannesRudolph]

Adds meshstack buildingblockrun logs <uuid>, buildingblockdefinition list and buildingblockdefinitionversion list.

• Logs have their own endpoint: a run object carries status only, no steps.
• --definition is required for versions. Reading a definition's versions takes a permission on the owning workspace, so a walk over all of them stops at the first foreign one with a 403.
• All three go through the Listing client and write the answer as the server sent it.

🤖 Generated with Claude Code

[meshcloud-gh-actions]

Coverage of the acceptance run against the meshStack backend, on 64da43caa6255d9839ac159d134825c753787548.

Scope	Coverage
Unit tests	66.1%
Acceptance tests	11.1%
Combined	66.1%

Uncovered functions

client/api_key.go:48: meshApiKeyClient.Create 0.0%
client/api_key.go:52: meshApiKeyClient.Read 0.0%
client/api_key.go:56: meshApiKeyClient.Update 0.0%
client/api_key.go:60: meshApiKeyClient.Delete 0.0%
client/api_key_permissions.go:21: ApiKeyPermissions.AllCodes 0.0%
client/api_key_permissions.go:34: ApiKeyPermissions.WorkspaceCodes 0.0%
client/api_key_permissions.go:50: ApiKeyPermissions.MarkdownString 0.0%
client/api_key_permissions.go:226: AllApiKeyPermissions 0.0%
client/api_key_permissions.go:231: WorkspacePermissionCodes 0.0%
client/building_block_definition.go:74: MeshBuildingBlockDefinitionApprovalPolicies.NothingRequiresApproval 0.0%
client/building_block_definition.go:85: DisabledSchedule 0.0%
client/building_block_definition.go:92: MeshBuildingBlockDefinitionSchedule.IsDisabled 0.0%
client/building_block_definition.go:97: MeshBuildingBlockDefinitionSpec.HasNeutralPolicies 0.0%
client/building_block_definition.go:102: MeshBuildingBlockDefinitionSpec.WithNeutralPolicies 0.0%
client/building_block_definition.go:171: meshBuildingBlockDefinitionClient.List 0.0%
client/building_block_definition.go:178: meshBuildingBlockDefinitionClient.ListRawSeq 0.0%
client/building_block_definition.go:185: meshBuildingBlockDefinitionClient.Read 0.0%
client/building_block_definition.go:189: meshBuildingBlockDefinitionClient.Create 0.0%
client/building_block_definition.go:193: meshBuildingBlockDefinitionClient.Update 0.0%
client/building_block_definition.go:197: meshBuildingBlockDefinitionClient.Delete 0.0%
client/building_block_definition_version.go:103: TagInputTargetsFor 0.0%
client/building_block_definition_version.go:248: meshBuildingBlockDefinitionVersionClient.List 0.0%
client/building_block_definition_version.go:254: meshBuildingBlockDefinitionVersionClient.ListRawSeq 0.0%
client/building_block_definition_version.go:260: meshBuildingBlockDefinitionVersionClient.Create 0.0%
client/building_block_definition_version.go:269: meshBuildingBlockDefinitionVersionClient.Update 0.0%
... and 163 more

covdata func names a method without its receiver, so an entry can belong to an implementation nothing selects rather than to a function the tests never reached. Open the file and line before reading one as a coverage gap.

[grubmeshi]

Superseded by #23, which brings this work together with #10, #11, #12 and #21, rebased on main and reviewed. I'm closing this PR by deleting its branch.