Omit token count in checkpoint metadata when no token data exists

[jcleira]

Summary

SessionMetadata.TotalTokens is an int that defaults to 0 when token tracking didn't occur, making it indistinguishable from a session that genuinely used 0 tokens. Change it to *int with omitempty so the field is absent when unknown.

Source

entireio/cli PR #854: "fix: omit token count when no token data exists"

Proposed Change

• Change SessionMetadata.TotalTokens from int to *int with json:"total_tokens,omitempty" in internal/checkpoint/metadata.go
• Only set the pointer in the post-commit hook when JSONL parsing actually found token usage data
• Display code in partio rewind --list treats nil as "unknown" and skips the token field rather than showing "0 tokens"

Why This Matters

Displaying "0 tokens" implies the agent ran but consumed no tokens — confusing and inaccurate. If a token count is shown, it should be real data.