chore: release v0.15.3

[edwin-zvs]

Bump version to 0.15.3 for patch release.

Changes since v0.15.2:

• feat(tui): graph context usage gauge (feat(tui): graph context usage gauge #930)
• feat: auto-title forks after first prompt (Auto-title forks after their first prompt #931)
• fix(daemon): deliver program fork prompts after harness startup settles (fix(daemon): deliver Program fork prompts after harness startup settles #929)
• fix(smith): allow long Codex OAuth streams (Fix 30-second cutoff for Codex OAuth streams #928)
• fix(smith): retry streams after partial reasoning (fix(smith): retry streams after partial reasoning #926)
• fix(daemon): suppress restart failure attention dots (fix(daemon): suppress restart failure attention dots #925)
• feat: context-usage gauge per session in the modeline (spec 0104) (feat: context-usage gauge per session in the modeline (spec 0104) #923)
• feat(tui): run Program selections in interactive forks (TUI: run Program selections in interactive forks #922)
• docs: harness integration checklist (docs: harness integration checklist (adding-a-harness.md) #924)
• feat(tui): lineage turn info shows token counts with hover detail (spec 0103) (feat(tui): lineage turn info shows token counts with hover detail (spec 0103) #921)
• fix: Add Escape as universal cancel fallback (Add Escape fallback for Construct cancel flows #919)
• feat: Show lineage after first message (Show TUI lineage after the first message #920)

Release steps:

1. Merge this PR
2. Tag merge commit as v0.15.3 and push tag