docs(ai-team): Milestone 4 planning - Chart component

Session: 2026-02-12-milestone4-planning
Requested by: Jeffrey T. Fritz

Changes:
- Logged session to .ai-team/log/2026-02-12-milestone4-planning.md
- Merged decisions from inbox (Chart.js evaluation, milestone plan, milestones directive)
- Propagated milestone 4 updates to 5 agent history files

Author: csharpfritz

.ai-team/agents/beast/history.md

@@ -30,3 +30,6 @@
 - **Sprint 3 docs delivered:** DetailsView and PasswordRecovery documentation created with full structure (features, Web Forms syntax, Blazor syntax, HTML output, migration notes, examples, See Also). Added to mkdocs.yml nav (alphabetical) and linked in README.md.
 
 📌 Team update (2026-02-12): Sprint 3 gate review — DetailsView and PasswordRecovery APPROVED. Action item: fix DetailsView docs to replace `DataSource=` with `Items=` in Blazor code samples. — decided by Forge
+
+ Team update (2026-02-12): Milestone 4 planned  Chart component with Chart.js via JS interop. 8 work items, design review required before implementation.  decided by Forge + Squad
+

.ai-team/agents/colossus/history.md

@@ -26,3 +26,6 @@
   - PasswordRecovery Step 1 uses `input[type='text']` for username, button for submit
 
 📌 Team update (2026-02-12): Sprint 3 gate review — DetailsView and PasswordRecovery APPROVED. 50/53 components (94%). Library effectively feature-complete. — decided by Forge
+
+ Team update (2026-02-12): Milestone 4 planned  Chart component with Chart.js via JS interop. 8 work items, design review required before implementation.  decided by Forge + Squad
+

.ai-team/agents/cyclops/history.md

@@ -43,3 +43,6 @@
 📌 Team update (2026-02-11): Sprint 3 scope: DetailsView + PasswordRecovery. Chart/Substitution/Xml deferred. 48/53 → target 50/53. — decided by Forge
 📌 Team update (2026-02-11): Colossus added as dedicated integration test engineer. Rogue retains bUnit unit tests. — decided by Jeffrey T. Fritz
 📌 Team update (2026-02-12): Sprint 3 gate review — DetailsView and PasswordRecovery APPROVED. 50/53 components (94%). — decided by Forge
+
+ Team update (2026-02-12): Milestone 4 planned  Chart component with Chart.js via JS interop. 8 work items, design review required before implementation.  decided by Forge + Squad
+

.ai-team/agents/forge/history.md

@@ -116,3 +116,36 @@
 - Library is effectively feature-complete for practical Web Forms migration
 
 📌 Team update (2026-02-11): Sprint 3 gate review — DetailsView APPROVED, PasswordRecovery APPROVED. 50/53 complete (94%). — decided by Forge
+
+### 2026-02-12 — Chart Component JS Library Evaluation
+
+**Requested by Jeffrey T. Fritz.** Performed full architectural evaluation of using a JavaScript charting library to implement the Web Forms `System.Web.UI.DataVisualization.Charting.Chart` control (previously deferred as "very high complexity").
+
+**Key findings:**
+- Web Forms Chart renders an `<img>` tag pointing to a server-generated PNG via `ChartImg.axd` — this is architecturally impossible to replicate in Blazor (no GDI+, no server-side image handler pipeline). Any implementation must accept a HTML output deviation.
+- The `SeriesChartType` enum has 35 chart types (Point through Pyramid). Realistic Phase 1 subset: 8 types (Column, Bar, Line, Pie, Area, Doughnut, Scatter, StackedColumn) covering 90%+ of real-world usage.
+- Chart's key sub-objects: Series, DataPoint, ChartArea, Axis, Legend, Title — must be mirrored as Blazor sub-components.
+
+**Library evaluation results:**
+- **D3.js — REJECTED.** Low-level SVG manipulation toolkit, not a charting library. Zero built-in chart types. No Blazor wrapper. Would require building an entire charting engine from scratch (XL effort). Jeffrey's suggestion, but wrong abstraction level.
+- **Chart.js — RECOMMENDED.** MIT license, ~60KB gzipped, ~10 built-in chart types covering all Phase 1 needs, multiple Blazor wrappers exist (though we recommend bundling chart.min.js directly and writing thin interop, not depending on community wrapper NuGet packages).
+- **ApexCharts — STRONG ALTERNATIVE.** MIT, ~120KB gz, 20+ chart types, official Blazor wrapper (Blazor-ApexCharts). Better coverage but double the bundle size and the wrapper has its own opinionated API.
+- **Plotly.js — REJECTED.** 3-4MB gzipped bundle size is disqualifying. Scientific/3D features are overkill.
+
+**Architecture recommendation:**
+- Use Chart.js bundled as a static asset (~60KB)
+- Thin JS interop layer (`chart-interop.js`) translating C# config → Chart.js config
+- Blazor Chart component mirrors Web Forms property names (Series, ChartAreas, etc.)
+- `<canvas>` output instead of `<img>` — documented as justified exception
+- Inherit `DataBoundComponent<T>` (consistent with Web Forms Chart inheriting DataBoundControl)
+- Effort: L (Large) — first component requiring JS interop, new testing challenges (canvas can't be bUnit-tested)
+
+**Risks identified:**
+1. JS interop is unprecedented in this project — new build/packaging complexity
+2. Canvas content not testable via bUnit — Playwright becomes primary quality gate
+3. Chart.js version pinning required — major version upgrades could break interop
+4. SSR/prerendering needs special handling (canvas requires DOM)
+
+**Recommendation: Proceed, but as Sprint 4** — not tacked onto Sprint 3. The JS interop pattern warrants dedicated design review and planning.
+
+📌 Team update (2026-02-12): Chart component feasibility confirmed — Chart.js recommended via JS interop. HTML output deviation (`<canvas>` not `<img>`) justified and documented. Effort: L. Target Sprint 4. — decided by Forge

.ai-team/agents/jubilee/history.md

@@ -42,3 +42,6 @@
 - **Nav ordering note:** Data Components section in NavMenu.razor is not strictly alphabetical (DataList before DataGrid). I placed DetailsView after DataGrid and before FormView to maintain the closest alphabetical order without rearranging existing entries.
 
 📌 Team update (2026-02-12): Sprint 3 gate review — DetailsView and PasswordRecovery APPROVED. 50/53 components (94%). — decided by Forge
+
+ Team update (2026-02-12): Milestone 4 planned  Chart component with Chart.js via JS interop. 8 work items, design review required before implementation.  decided by Forge + Squad
+

.ai-team/agents/rogue/history.md

@@ -25,3 +25,6 @@
 📌 Test pattern: DetailsView is a generic DataBoundComponent<ItemType> — tests must use `ItemType="Widget"` and provide `Items` parameter as a list. PasswordRecovery requires NavigationManager service registration (`Services.AddSingleton<NavigationManager>(new Mock<NavigationManager>().Object)`). Both follow the .razor test file pattern inheriting BlazorWebFormsTestContext via _Imports.razor. — Rogue
 
 📌 Team update (2026-02-12): Sprint 3 gate review — DetailsView and PasswordRecovery APPROVED. 71 new tests verified. 797 total. — decided by Forge
+
+ Team update (2026-02-12): Milestone 4 planned  Chart component with Chart.js via JS interop. 8 work items, design review required before implementation.  decided by Forge + Squad
+