docs(roadmap): Timeline and Clip Deck are complete in v3.1.5

[CaYatur]

Found by the owner before tagging.

• The bug: the v3.1.5 column in the ROADMAP status table copied v3.1.4's partial marks for Timeline and Clip Deck.
• Why that was wrong: the gaps named in their notes were all closed in this release.
  • Timeline: multi-select (feat(timeline): multi-select, loop brace, marker drag, fade handles, full window #648) and tempo changes on the ruler (Timeline: tempo changes on the ruler, lane height; the BPM field no longer wipes the tempo map #662).
  • Clip Deck: several decks (feat(clipdeck): launch modes, grid keyboard, drag and drop, several decks #649), and video, image and shader slots (feat(clipdeck): video, image and shader slots apply to a chosen target #651).
• Change:
  • Timeline and Clip Deck now show ✅ for v3.1.5, with notes describing what Timeline: a larger, professional editor #636 and Clip Deck: a clearer, more reliable performance grid #637 brought.
  • The Text and lyrics, Now Playing and Multi-monitor notes name what v3.1.5 added.

Full suite 2999/2999.

Refs #695

[cayadraft]

@CaYatur

CaYaDraft — pull request

Summary
This pull request corrects the ROADMAP status table in ROADMAP.md to accurately reflect that Timeline and Clip Deck features are complete in version v3.1.5, replacing incorrect partial marks from the previous release. The update also ensures other feature notes correctly describe the changes introduced in this specific version.

Files

• ROADMAP.md (corrected status for v3.1.5)

Note
Nothing blocking is visible from the text.

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Stopping here. I will not merge, push, or change this pull request until you ask.

/caya explain describes the diff. /caya plan previews the next edit. /caya revise adds a commit.