[bug]: Kiro CLI mutable request deltas stay in the start bucket across days

[pitimon]

Bug

Kiro CLI live requests are mutable cumulative snapshots. TokenTracker computes positive per-request growth correctly but always applies every later delta to the immutable request_start_timestamp_ms bucket.

A request that remains active across midnight therefore grows its start-day total.

Evidence

• parseKiroCliIncremental() reads cumulative prompt/response sizes and stores a per-request watermark.
• want.bucketStart is derived from request_start_timestamp_ms.
• The positive delta at the watermark application stage is always added to want.bucketStart.
• Existing mutation coverage grows one request while retaining the start timestamp, but does not cross midnight.

Expected policy

• First positive contribution: request-start bucket.
• Later positive growth for an existing request: current sync observation bucket.
• Preserve watermark adoption, migration, reset/degraded-read behavior, conversation counts, and token conservation.
• Add deterministic cross-midnight regression coverage.

Confirmed by provider-wide audit after Hermes #154 and Goose #158. Affected through v0.39.47.

[pitimon]

Reopening because PR #172 was a standards-routing pilot only. It did not implement or verify the Kiro mutable-request delta/timestamp fix described by this issue. The prior closure at merge time was accidental; this issue remains part of the #164–#166 parser pilot evidence set and still requires its own TDD implementation PR.