Deprecate the entire checkpoints v2 migrate command

[computermode]

https://entire.io/gh/entireio/cli/trails/389

The v1 -> v2 checkpoint migration is no longer recommended. This replaces the v2 migration command with a stub that prints "Migration to checkpoints v2 has been halted for now." and exits non-zero for any invocation, and remove the push-time hint that recommended running it. compactTranscriptForStartLine moves into attach.go (its only remaining caller), and the now-unused progressBar helper is dropped.

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Note

Medium Risk
Changes runtime CLI behavior by turning the hidden entire migrate flow into a hard-failing stub and removing push-time migration guidance; low code complexity but could impact users relying on migration/recovery workflows.

Overview
Deprecates v2 checkpoint migration. Replaces the hidden entire migrate implementation with a stub that disables flag parsing, prints a deprecation message, and exits non-zero; the large v1→v2 migration code and its test suite are removed.

Cleans up related UX and utilities. Removes the push-time hint that recommended running migration, drops the now-unused terminal progressBar helper, and moves compactTranscriptForStartLine into attach.go (its remaining caller). Also updates doctor’s disconnected /main check to default to remote origin.

^{Reviewed by Cursor Bugbot for commit 0baffbd. Configure here.}

[Copilot]

Pull request overview

This PR deprecates the hidden v1-to-v2 checkpoint migration path by replacing the migrate implementation with a failing stub and removing push-time hints that recommended running it.

Changes:

• Replaced entire migrate with a hidden, non-zero deprecation stub.
• Removed the v2 migration hint from push flows and deleted the now-unused progress bar helper.
• Moved compact transcript generation helper into attach.go and updated related references.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
cmd/entire/cli/strategy/push_v2.go	Removes v2 migration hint calls after v2 push outcomes.
cmd/entire/cli/strategy/push_common.go	Deletes migration hint helpers and removes remaining hint calls.
cmd/entire/cli/strategy/push_common_test.go	Removes tests for deleted migration hint logic.
cmd/entire/cli/progress.go	Removes unused progress bar implementation.
cmd/entire/cli/migrate.go	Replaces migration implementation with deprecated stub command.
cmd/entire/cli/migrate_test.go	Deletes previous migration test suite.
cmd/entire/cli/doctor.go	Replaces removed migrate remote constant with origin.
cmd/entire/cli/attach.go	Adds compact transcript helper now used by attach flow.