[WIP] Boot-disk repartition for in-field EVE-kvm ↔ EVE-k conversion

[eriknordmark]

Boot-disk repartition for in-field EVE-kvm ↔ EVE-k conversion

Long-lived devices installed with EVE's old small boot-disk layout (IMGA/IMGB
as small as 300 MB, a small ESP) cannot hold the EVE-k (Kubernetes) rootfs and
its container/k3s tooling. Upgrading replaces rootfs contents but never
repartitions, so the small geometry persists. This branch repartitions the boot
disk in place to the larger EVE-k geometry at the moment the controller pushes a
cross-flavor base-OS update — growing ESP/IMGA/IMGB, and first shrinking the
/persist filesystem when that's the only way to free the space — so an
in-field device can be converted to EVE-k without re-imaging and without losing
/persist data or device identity.

A read-only pre-flight classifies the disk into proceed / grow / shrink /
insufficient. grow happens online; shrink backs up the device identity to
the CONFIG partition and reboots into an offline shrink+grow under storage-init;
insufficient declines the conversion cleanly and the device stays on its
current flavor. The design is idempotent and fail-safe: no failure mode bricks
the device, and even a power loss mid-shrink recovers to a bootable, remotely
manageable state.

See docs/STORAGE-RESIZING.md for the full design.

What's here

• pkg/storage-resizer — standalone Go binary doing all the disk work
  (check/backup/shrink/grow/restore/cleanup) via diskfs/partitionresizer, kept
  out of the pillar module.
• storage-init — runs the offline shrink/grow and post-mount
  restore/cleanup, re-syncing /config so PCR14 stays stable.
• pkg/pillar/diskconvert — pillar orchestration that execs the resizer and
  selects the next step; unit-tested behind a fake Runner.
• baseosmgr / nodeagent / zedagent — drive the conversion at the cross-flavor
  seam, reboot into the offline shrink when needed, and report
  ZDEVICE_STATE_CONVERTING with a sub-state.
• volumemgr / upgradeconverter — recognize blobs already on /persist across
  the kvm→k namespace change so pre-staged content isn't re-downloaded; gate the
  cross-flavor block on the actual volume set.

PR dependencies

• volumemgr: persist deferred content-tree deletes #6085 (volumemgr: persist deferred content-tree deletes) — the conversion
  relies on the deferred content-tree delete to preserve CAS blobs across the
  conversion reboot, so an app/base image isn't re-downloaded after the kvm→k
  switch.
• info: add ZDEVICE_STATE_CONVERTING state and ZDeviceSubState eve-api#149 — vendored ZDEVICE_STATE_CONVERTING / ZDeviceSubState
  (hand-carried until it merges; see below).

Draft — in-flight items before merge

• pkg/pillar/vendor hand-carries the eve-api ZDEVICE_STATE_CONVERTING /
  ZDeviceSubState change; switch to make bump-eve-api once
  info: add ZDEVICE_STATE_CONVERTING state and ZDeviceSubState eve-api#149 merges.
• Full end-to-end test plan still needs to be executed — the on-device
  conversion (grow and shrink+grow paths, and the power-loss recovery cases) has
  not yet been run through to completion on this branch.

How to test and validate this PR

Draft — the full on-device test plan has not yet been executed (see the
in-flight items above). Intended validation:

• Unit: pkg/pillar/diskconvert orchestration tests (fake Runner) and the
  pkg/storage-resizer check/shrink/grow logic.
• E2E under eden + swtpm on a device installed with the old small boot-disk
  geometry: push a cross-flavor (EVE-kvm→EVE-k) base-OS update and confirm
  each pre-flight class behaves correctly — grow (online), shrink
  (offline shrink+grow under storage-init, identity backed up to CONFIG and
  restored), and insufficient (conversion declined cleanly, device stays on
  its current flavor). Confirm /persist data and device identity survive,
  and that a power loss mid-shrink recovers to a bootable, remotely
  manageable state.

Changelog notes

Adds in-field boot-disk repartitioning so a device installed with EVE's old
small boot-disk layout can be converted between EVE-kvm and EVE-k on a
cross-flavor base-OS update, without re-imaging and without losing /persist
data or device identity.

PR Backports

• 16.0-stable: No.
• 14.5-stable: No.
• 13.4-stable: No.

Checklist

• I've provided a proper description
• I've added the proper documentation
• I've tested my PR on amd64 device
• I've tested my PR on arm64 device
• I've written the test verification instructions
• I've set the proper labels to this PR

And the last but not least:

• I've checked the boxes above, or I've provided a good reason why I didn't
  check them.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 28.86435% with 451 lines in your changes missing coverage. Please review.
✅ Project coverage is 23.05%. Comparing base (74ffe8e) to head (31a5c88).
⚠️ Report is 38 commits behind head on master.

Files with missing lines	Patch %	Lines
pkg/pillar/cmd/baseosmgr/convert.go	20.90%	140 Missing ⚠️
pkg/pillar/vault/handler_zfs.go	2.22%	88 Missing ⚠️
pkg/pillar/cmd/baseosmgr/baseosmgr.go	0.00%	49 Missing ⚠️
pkg/pillar/diskconvert/convert.go	46.66%	48 Missing ⚠️
...illar/cmd/upgradeconverter/containerd_namespace.go	71.68%	20 Missing and 12 partials ⚠️
pkg/pillar/cmd/nodeagent/handlebaseos.go	0.00%	18 Missing ⚠️
pkg/pillar/cmd/nodeagent/nodeagent.go	0.00%	18 Missing ⚠️
pkg/pillar/cmd/baseosmgr/handlebaseos.go	0.00%	17 Missing ⚠️
pkg/pillar/cmd/zedagent/reportinfo.go	0.00%	13 Missing ⚠️
pkg/pillar/zfs/zfs.go	0.00%	13 Missing ⚠️
... and 3 more

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6063      +/-   ##
==========================================
+ Coverage   22.64%   23.05%   +0.41%     
==========================================
  Files         507      520      +13     
  Lines       93195    95539    +2344     
==========================================
+ Hits        21103    22030     +927     
- Misses      70367    71586    +1219     
- Partials     1725     1923     +198     

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