fix(components): let the Code Collab file index retry after a failure

[pythonlearner1025]

Once the file-index acquisition fails, "Files unavailable" is terminal. The
effect keys on {cache, flockDocId, loadLocalSnapshot, prepareTarget} and a
reconnect changes none of them, so it never runs again; closing and reopening the
panel restores the whole tree, which shows only the effect is stuck. The panel
offers no way out either: the Try again action exists on the local-error
branch and on no other.

• useCodeCollabFileIndexLoadState takes a reloadNonce, joined into the
  existing requestKey, so bumping it re-runs the acquisition exactly as a
  changed cache or doc id would.
• useCodeCollabSessionFileProvider returns reload, and re-arms itself on an
  offline -> online transition of the owning machine. A transition, never a
  status: "retry while the status is error" loops for ever against a machine that
  is online and answering errors, while an edge fires at most once per outage.
• FileTreeView takes onProviderRetry and gives the provider-unavailable panel
  the same RefreshCw + sessions.codeSession.files.retry action the
  local-error panel already draws. Callers that pass nothing see no button.
• SessionDetail passes the provider's reload.

Compatibility

Every change is additive at its default. With the new prop, parameter or flag
absent, the touched components render and behave exactly as they do today, and
no existing call site in this repository passes one.

Testing

packages/components typecheck and the full vitest suite pass. No new test: the acquisition effect needs a runtime and a Flock document. The offline→online re-arm is the part most worth a test and is the one that needs the most scaffolding; happy to add it if you point at the harness you would want it in.

Notes for the reviewer

The re-arm fires on a TRANSITION, never on a status: "retry while the status is error" loops for ever against a machine that is online and answering errors.

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Review metadata

BlitzOS fork only. Delete this section before sending the PR to LodyAI/Lody.

Branch	blitz/seam-10-file-index-retry
Branched from	f3474894 (the pinned upstream commit)
Classification	A — upstream bug fix
Suggested submit priority	P1
Vendor seam patch	10 (BUG-2)

.../sessions/components/file-tree-view.tsx         | 16 ++++++
 .../src/components/sessions/session-detail.tsx     |  3 ++
 .../hooks/use-code-collab-session-file-provider.ts | 57 ++++++++++++++++++++--
 3 files changed, 72 insertions(+), 4 deletions(-)