2.0 pre and post-release work

[klebba]

Tasks to complete pre-release

• ✅ Remove support for ifDefined and repeat directives (and associated tests, docs, etc) — [updated 2025-12-03] implemented in Ditch Deprecated Directives (e.g., “ifDefined”). #335.
• ✅ Remove support for custom template engines (and associated tests, demos, etc) — [updated 2025-12-03] implemented in Remove custom template engine support. #338.
• ✅ Ensure properties exist on the instance at construction time (React interop enhancement, also forward looking toward future class decorator support) — [updated 2025-12-03] implemented in Initialize properties in constructor for React. #332.
• ✅ Decide: remove support for ifDefined and repeat, or continue to support as deprecated features (and all related work, e.g. removing comments and other complexity) — [updated 2025-12-02] team decides to remove support completely in 2.0
• ✅ Decide: should we drop support for custom template engines? — [updated 2025-12-02] team decides to remove support completely in 2.0
• ✅ Decide: what happens when you call "render" before onConnected (throw vs do it) — [updated 2025-12-02] team decides to fix the bug (do it, do not throw)

Tasks to complete post-release — #215

• Fix the render-before-onConnected lifecycle woe
• Symbol.toStringTag implementation Consider leveraging “Symbol.toStringTag” to print constructor name of element when cast as string. #317
• Rethink definition-time analysis routine (versus lazy time): we are doing a lot of heavy lifting during the "import waterfall" / and testing elements uncovers some "code smell" regarding when analysis happens - it would be preferable to isolate analysis from registration. We could do "lazy analysis" instead
• Decide: rename project to "custom elephant 🐘"?
• ✅ Think about the future of DocumentFragment support (e.g. reuse of doc frags is a confusing thing if you have forgotten their intrinsic behavior - so uhhh... do not forget it) — [updated 2025-12-03] this work has actually already been discussed and implemented, see Allow binding empty “DocumentFragment” instances. #312

Post-release housekeeping

• review docs; simplify, clarify
• review error messages; we have a list in Minor language tweaks to x-parser error language #248
• provide more pragmatic examples in /docs/EXAMPLES.md or similar
• unleash Claude on the source
• review array and map validation (e.g., we could relax errors in some cases)