fix(story): require release-style active summary for open-turn publish

[mosure]

Motivation

• A recent change allowed active_progress_summary to bypass the stricter open-turn gate in compile_active_update, enabling transcript-derived assistant lines to become publishable active-update stories before turn completion and risking private context disclosure.
• The intent of this change is to restore the prior privacy boundary by requiring the release/outcome-style active_update_summary predicate for open-turn publication.

Description

• Removed the alternate acceptance path active_progress_summary_for_project(...) from StoryCompiler::compile_active_update so open-turn flushes only proceed when active_update_summary_for_project(...) passes.
• Non-qualifying summaries continue to use the existing fallback compile_activity_checkpoint(...), preserving non-sensitive progress signaling without publishing transcript-derived active updates.
• Updated the unit test to active_progress_message_does_not_publish_without_turn_completion and changed its assertion to ensure active-progress-only messages do not publish before turn completion.
• Ran cargo fmt --all to apply formatting changes.

Testing

• Ran cargo fmt --all and it completed successfully.
• Ran cargo +1.92.0 test -p agent_feed_story active_progress_message_does_not_publish_without_turn_completion --ignore-rust-version --offline -- --nocapture and the test passed.
• Ran cargo +1.92.0 test -p agent_feed_story meaningful_agent_message_publishes_after_flush --ignore-rust-version --offline -- --nocapture and the test passed.
• Note: the repository enforces a newer rustc version; tests were executed with cargo +1.92.0 and --ignore-rust-version to run in the validation environment.

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Codex Task