feat(tui/ecosystem): role.md detail surface + searchable role table (proposal 003 PR-2)

[flg77]

Summary

PR-2 of proposal 003 (ACC TUI usability hardening). Addresses operator review items 1, 2, 3 from ACC TUI Review.md:

#	Operator complaint	Resolution
1	Role detail box doesn't show role.md content — only role.yaml	New Markdown widget renders role.md content alongside the existing yaml view
2	Role overview too long / fixed-size — needs to be browsable	Detail panel split into two Collapsible widgets inside the existing ScrollableContainer
3	Add a search bar for roles	New Input(#role-filter) above the role DataTable; case-insensitive substring match against name / domain / persona

Wire shape

ROLE LIBRARY
  [Filter…………………………………………………]   <- new
  [DataTable: Role / Domain / Persona / Tasks]

ROLE DETAIL
  ▼ role.md (narrative)              <- new, open by default
    [Markdown render of role.md]
  ▶ role.yaml (raw)                  <- collapsed by default
    [Static yaml content — unchanged]

Changes

acc/tui/screens/ecosystem.py

• Compose: Input(#role-filter) added above the role DataTable; the single Static(#role-detail-panel) replaced with a placeholder + two Collapsible widgets (#role-md-collapsible + #role-yaml-collapsible).
• _load_roles() caches loaded rows in self._all_role_rows; delegates to _apply_filter("") for the initial render.
• _apply_filter(query) rebuilds the DataTable from the cache keeping only matching rows.
• on_input_changed(event) reacts to keystrokes in #role-filter.
• _show_role_detail(role_name) reads role.md alongside role.yaml; renders via the Markdown widget.
• New _read_role_md(md_path, role_name) helper with friendly-fallback placeholder when role.md is absent (points operators at slot 006's forthcoming authoring guideline).

Tests

• tests/test_ecosystem_screen_pilot.py — _capture_panel_updates() now taps both new surfaces so the prior substring assertions keep passing. 5 new tests cover the md surface (present + absent) and the filter (narrow / persona-match / no-match).
• tests/test_coding_agent_tui_pilot.py — one-line update to read from #role-yaml-content instead of the removed #role-detail-panel.

25/25 tests green across the ecosystem + coding-agent TUI test files.

CHANGELOG note

PR-2's [Unreleased] CHANGELOG entries will be added during rebase once PR #54 (which introduces CHANGELOG.md) lands. Skipping the file here avoids a guaranteed merge conflict on a file that doesn't yet exist on main.

Manual verification

acc-tui    # navigate to Ecosystem (key 6)
# Type substring in filter → only matching rows render; clear → full list restored
# Click any role → role.md renders in the open collapsible at top
# Click the role.yaml collapsible → raw yaml renders identically to before
# Roles without role.md show the authoring-guidance placeholder

Reference

Proposal 003 — …\ACC Implementation\003 - ACC TUI usability hardening.md (operator vault).

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