M7: Mark Steps and Harness Sessions with dividers and use plain labels

[Sandstorm831]

Parent

Spec #276; implementation sub-issue of M7 #275.

What to build

A thin divider marks where each Step begins, naming the Step in plain words, and a visibly different divider marks where each Harness Session begins, naming the conversation; they differ in glyph and wording, not only colour, and fit ADR 0036's thin rule naming the Step and its Harness Session. Everyday rows use plain words: no "session spec"-style labels, no Session availability words such as open, detached, or unusable, and plain labels for raw event kinds. Session availability stays in the details panel (stories 80–85).

Acceptance criteria

• Renderer tests prove both dividers, their plain wording, and their distinct glyphs with colour off.
• Renderer tests prove everyday rows carry no internal Session labels or availability words, and the details panel still shows availability.
• Dividers wrap and scroll like other rows without breaking anchor or new-activity count.
• Prototype Crucible's launch and Run information architecture #23 evidence: keymap and focus, small terminals and resize, large content, interaction tuning, meaning without colour, and renderer and platform evidence, each shown by testRender frames with the fake Renderer Port.
• CI scenario: the transcript renderer tests are green on Windows x64, macOS arm64, and Linux x64.

Blocked by

• M7: Report structural violations from one rule catalogue in a dedicated gate step #277
• M7: Report guidance-structure violations in the contract and check Module guidance shape #278
• M7: Report vendor-provenance violations in the contract #279
• M7: Report release-workflow violations in the contract #280
• M7: Enforce unused code and clear today's findings #281
• M7: Fail lint on any warning and add two OpenCode style rules #282
• M7: Wrap transcript and timeline lines instead of clipping them #288

Implementation packet

Owner: TUI presentation (timeline rows, Workbench views, details panel)

Ratchet: renderer tests for Step and Session dividers and plain labels

Deletes: "session spec"-style labels and availability words on everyday rows

Gate: ADR 0027 three-OS CI and recorded human evidence, with the slice scenario above.

Dependencies: no new runtime dependency