fix(memory): preserve goal run start metadata - #7153

Summary

• preserve the original goal run started_at value across ordinary state upserts
• replace a terminal predecessor with a fresh run and fresh started_at in one atomic SQLite upsert
• remove the delete-then-insert crash window from goal restarts
• validate phases and RFC3339 timestamps at the store boundary before SQLite writes
• order recovery rows by parsed timestamps with a deterministic goal-ID tie-breaker
• describe PASSIVE WAL checkpoints as best-effort instead of a durability barrier

Verification

• CARGO_INCREMENTAL=0 CARGO_TARGET_DIR=/Volumes/Lexar/worktrees/target-7153 cargo test -p librefang-memory goal_run_store --lib — 13 passed
• CARGO_INCREMENTAL=0 CARGO_TARGET_DIR=/Volumes/Lexar/worktrees/target-7153 cargo test -p librefang-kernel start_replaces_terminal_row_with_a_fresh_started_at --lib — 1 passed
• cargo fmt --all -- --check
• git diff --check origin/main...HEAD

Out of scope

• changing the public GoalRunRow field types across crates
• migrating already persisted malformed timestamps
• changing WAL synchronous or checkpoint policy