feat: Expose per-mount subpath/alias/permission on legacy ComputeSession GraphQL node

[rapsealk]

Summary

The current WebUI still consumes the legacy Graphene GraphQL schema, where a session only exposes mounts (vfolder names) and vfolder_mounts (vfolder UUIDs) — both of which drop per-mount details such as the mounted subpath, the in-container mount destination (alias), and the granted permission.

This PR adds a read-only vfolder_mount_infos field to the legacy ComputeSession and ComputeSessionNode types, surfacing those per-mount details directly from the stored VFolderMount objects (via row.vfolders_sorted_by_id) so the UI can render them without waiting for the SessionV2 migration.

This is a deliberate, scoped exception to the v2-first rule, justified by the UI still consuming the legacy schema. It is limited to read-only mount fields.

New type VFolderMountInfo

GraphQL field	Source (VFolderMount / VFolderMountData)	Notes
vfolder_id	str(m.vfid.folder_id)
name	m.name
subpath	str(m.vfsubpath)	null when mounting the vfolder root (".")
mount_destination	str(m.kernel_path)	alias / container mount path
permission	m.mount_perm.value
usage_mode	m.usage_mode.value

The existing mounts and vfolder_mounts fields are unchanged for backward compatibility. The new field is populated at every construction site: ComputeSessionNode.from_row, ComputeSessionNode.from_dataclass, and ComputeSession.parse_row.

Test plan

• pants fmt --changed-since=main
• pants fix --changed-since=main
• pants lint --changed-since=main
• pants check --changed-since=main
• pants test --changed-since=main
• GraphQL schema regenerated (scripts/generate-graphql-schema.sh); schema.graphql and supergraph.graphql updated
• Unit test added (tests/unit/manager/test_vfolder_mount_info.py) covering the per-mount mapping helper, including the subpath == "." → null case and custom mount_destination/permission
• Live server verification pending

Part of #11962
Resolves #11964

🤖 Generated with Claude Code

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📚 Documentation preview 📚: https://sorna--11967.org.readthedocs.build/en/11967/

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📚 Documentation preview 📚: https://sorna-ko--11967.org.readthedocs.build/ko/11967/

[Copilot]

Pull request overview

This PR extends the legacy Graphene (v1) GraphQL ComputeSession and ComputeSessionNode types with a new read-only vfolder_mount_infos field so the current WebUI can access per-mount vfolder metadata (subpath, in-container destination/alias, permission, usage_mode) that is already persisted on sessions but not exposed in the legacy schema.

Changes:

• Added a legacy Graphene output type VFolderMountInfo plus mapping helpers to convert stored VFolderMount / VFolderMountData entries into GraphQL-friendly objects (including "." → null normalization for root subpath).
• Populated vfolder_mount_infos from all legacy ComputeSession construction paths (ComputeSessionNode.from_row, ComputeSessionNode.from_dataclass, ComputeSession.parse_row) without modifying existing mounts / vfolder_mounts.
• Regenerated the published GraphQL schema docs and added unit tests for the mount-info mapping behavior.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
tests/unit/manager/test_vfolder_mount_info.py	Adds unit tests validating the mount-to-GraphQL mapping and "." → null subpath normalization.
src/ai/backend/manager/api/gql_legacy/session.py	Introduces VFolderMountInfo, mapping helpers, and exposes vfolder_mount_infos on legacy session types.
docs/manager/graphql-reference/supergraph.graphql	Updates the federated supergraph schema docs to include the new field and type.
docs/manager/graphql-reference/schema.graphql	Updates the legacy schema docs to include the new field and type.

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[github-actions]

This PR has had no activity for 14 days and has been marked as stale. It will be closed on 2026-07-09 (in 14 days) if no further activity occurs. Push a commit or leave a comment to keep it open.

[seedspirit]

Rather than expanding legacy graphene based schema, let's migrate to v2 schema(based on strawberry)