Add per-phase perf spans to checkpoint pre-push

[computermode]

https://entire.io/gh/entireio/cli/trails/439

Break the single push_checkpoints_branch span into nested child spans so entire doctor trace --hook pre-push shows where time goes during a slow checkpoint push instead of one total:

• resolve_push_settings: settings load + the one-time metadata-branch fetch (fetchMetadataBranchIfMissing), otherwise invisible.
• push_checkpoints_branch > git_push (+ git_push~1 for the retry): the actual git push subprocess, where time goes on a slow transport. Records an error flag on non-fast-forward rejection, which signals the recovery path was taken.
• push_checkpoints_branch > fetch_and_rebase > git_fetch: the sync recovery path, splitting the network fetch from the local rebase.

Threads the push span's context through pushBranchIfNeeded so the child steps nest correctly. Instrumentation only; no behavior change.

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Note

Low Risk
Observability-only changes to pre-push; no push, fetch, or rebase logic altered.

Overview
Adds nested perf spans around checkpoint pre-push so traces (e.g. entire doctor trace --hook pre-push) show where time is spent instead of one opaque push_checkpoints_branch block.

PrePush now spans resolve_push_settings (including one-time metadata-branch fetch during remote resolution) and passes span context into pushBranchIfNeeded so children nest under push_checkpoints_branch.

push_common.go adds git_push around each push attempt (retries appear as a second span), fetch_and_rebase around sync recovery, and git_fetch inside fetch+rebase. Errors are recorded on spans where relevant. No functional change—instrumentation only.

^{Reviewed by Cursor Bugbot for commit 5d555f9. Configure here.}

[Copilot]

Pull request overview

Adds finer-grained perf instrumentation to the checkpoint pre-push flow so entire doctor trace --hook pre-push can attribute time to specific phases (settings/remote resolution, the actual git push attempts, and fetch+rebase recovery) rather than a single opaque span.

Changes:

• Introduces a resolve_push_settings span around settings load + possible one-time metadata-branch fetch during remote resolution.
• Threads the parent push span context into pushBranchIfNeeded so subsequent spans nest under push_checkpoints_branch.
• Splits push/recovery work into nested spans: git_push per push attempt, fetch_and_rebase for the sync recovery path, and git_fetch within that path.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
cmd/entire/cli/strategy/push_common.go	Adds child perf spans for git_push, fetch_and_rebase, and git_fetch to improve trace granularity during checkpoint push and recovery.
cmd/entire/cli/strategy/manual_commit_push.go	Adds a resolve_push_settings span and ensures push span context is propagated so nested push/recovery spans attach correctly.