docs: orchestrator close-out IUV-M02 (#445)

docs/scratchpads/install-ux-v2-20260405.md

@@ -146,3 +146,28 @@ Worker's initial approach added `vitest.config.ts` to `apps/gateway/tsconfig.jso
 
 - Close out orchestrator doc sync (this commit): mark M01 subtasks done in `TASKS.md`, update manifest phase to Execution, commit scratchpad session 2, PR to main.
 - After merge, delegate IUV-M02 (sonnet, isolated worktree). Dependencies: IUV-02-01 (CORS→FQDN) starts unblocked since M01 is released; first real task for the M02 worker is diagnosing the skill installer failure modes (IUV-02-02) against the fresh 0.0.26 install.
+
+## Session 3 — 2026-04-05 (IUV-M02 delivery + close-out)
+
+### Outcome
+
+IUV-M02 shipped. PR #444 merged (`172bacb3`), issue #437 closed. 18 new tests (13 CORS derivation, 5 skill sync).
+
+### Changes
+
+**CORS → FQDN (IUV-02-01):**
+
+- `packages/mosaic/src/stages/gateway-config.ts` — replaced raw "CORS origin" text prompt with "Web UI hostname" (default: `localhost`). Added HTTPS follow-up for remote hosts. Pure `deriveCorsOrigin(hostname, port, useHttps?)` function exported for testability.
+- Headless: `MOSAIC_HOSTNAME` env var as friendly alternative; `MOSAIC_CORS_ORIGIN` still works as full override.
+- `packages/mosaic/src/types.ts` — added `hostname?: string` to `GatewayState`.
+
+**Skill installer rework (IUV-02-02 + IUV-02-03):**
+
+- Root cause confirmed: `syncSkills()` in `finalize.ts` ignored `state.selectedSkills` entirely. The multiselect UI was a no-op.
+- `packages/mosaic/src/stages/finalize.ts` — `syncSkills()` rewritten to accept `selectedSkills[]`, returns typed `SyncSkillsResult`, passes `MOSAIC_INSTALL_SKILLS` (colon-separated) as env var to the bash script.
+- `packages/mosaic/framework/tools/_scripts/mosaic-sync-skills` — added bash associative array whitelist filter keyed on `MOSAIC_INSTALL_SKILLS`. When set, only whitelisted skills are linked. Empty/unset = all skills (legacy behavior preserved for `mosaic sync` outside wizard).
+- Failure surfaces: silent `catch {}` replaced with typed error reporting through `p.warn()`.
+
+### Next action
+
+- Delegate IUV-M03 (opus, isolated worktree) — the architectural milestone: provider-first intelligent flow, drill-down main menu, Quick Start fast path, agent self-naming. This is the biggest piece of the mission.