Plan, progress, and TUI improvements for planetscale

[aparajon]

• Parallel plan — schema fetching and diffing now run with up to 20 concurrent goroutines per keyspace, reducing plan time for 30+ keyspace databases from serial to ~2s
• Collapse identical keyspaces — when 6+ consecutive keyspaces have the same DDL changes, plan output shows the first 3 headers then "... and N more keyspaces with identical changes" with the DDL printed once
• Schema API routing — plan uses PlanetScale schema API when safe_migrations is enabled on the branch, vtgate when disabled. Removed the api-plan fake environment hack
• Keyspace progress — namespace preserved through engine progress, local task sync, and terminal rendering so duplicate table names across keyspaces show correct headers
• TUI error display — failed applies now show the error message in red with recovery guidance instead of silent ❌ Failed
• LocalScale deploy scoping — deploy request allocation, lookup, updates, and processor transitions scoped by org/database/number

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes PlanetScale planning accuracy by selecting the correct “current schema” source based on whether safe schema changes are enabled, and it makes progress reporting keyspace-aware so duplicate table names across Vitess keyspaces are tracked and rendered correctly.

Changes:

• Choose PlanetScale plan “current schema” source based on branch safe-migrations mode (API when enabled, vtgate when disabled).
• Preserve and use namespace/keyspace in engine progress → task syncing → UI/API rendering to avoid collisions on duplicate table names.
• Add LocalScale safe_migrations config and Docker-backed integration tests covering both schema-source paths.

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pkg/tern/progress_keys.go	Adds shared (tern-local) namespace/table keying helpers for progress lookup.
pkg/tern/progress_keys_test.go	Unit tests ensuring namespace-aware progress matching and fallback behavior.
pkg/tern/local_control.go	Uses namespace-aware progress matching when snapshotting and applying engine progress to tasks.
pkg/tern/local_client.go	Uses namespace-aware engine progress mapping for terminal progress rendering and task selection tweaks.
pkg/tern/local_apply.go	Uses namespace-aware per-table progress when syncing atomic tasks from engine results.
pkg/localscale/testcontainer.go	Extends container DB config to allow toggling safe_migrations.
pkg/localscale/server_integration_test.go	Adds databases/keyspaces to test safe-migrations enabled/disabled behavior in containerized LocalScale.
pkg/localscale/server.go	Plumbs SafeMigrations config through to backend state with a default of true.
pkg/localscale/handlers_branches.go	Returns correct safe_migrations value in branch responses (including virtual main).
pkg/localscale/planetscale_engine_integration_test.go	Integration test validating plan schema source selection (API vs vtgate) and error behavior without DSN.
pkg/engine/engine.go	Adds Namespace field to engine.TableProgress for keyspace-aware progress.
pkg/engine/planetscale/planetscale.go	Adds schema-source selection logic and vtgate schema fetch implementation; includes namespace in aggregated progress.
pkg/api/progress_handlers.go	Makes API progress/task correlation namespace-aware and preserves keyspace in responses.
pkg/api/progress_handlers_test.go	Tests keyspace preservation for terminal applies and namespace-aware sync from Tern progress.
cmd/localscale/main.go	Adds safe_migrations to LocalScale config parsing and wiring.

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