docs: update documentation to match current implementation

- SKILLS.md: Update roadmap phases with actual completion status
  - Phase 0-1 complete, Phase 2-5 partial, resolved design decisions
- OVERVIEW.md: Add HttpServer, Test effect, JIT to completed features
- ROADMAP.md: Add HttpServer, Process, Test effects to done list
- VISION.md: Update Phase 2-3 tables with current status
- guide/05-effects.md: Add Time, HttpServer, Test to effects table
- guide/09-stdlib.md: Add HttpServer, Time, Test effect docs
- reference/syntax.md: Fix interpolation syntax, remove unsupported literals
- testing.md: Add native Test effect documentation

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/reference/syntax.md

@@ -31,18 +31,15 @@ Examples: `foo`, `myVar`, `Type`, `Option`
 42
 -17
 1_000_000      // Underscores for readability
-0xFF           // Hexadecimal
-0b1010         // Binary
 
 // Floats
 3.14
-2.5e10
--1.5e-3
+-1.5
 
 // Strings
 "hello"
 "line1\nline2"              // Escape sequences
-"value: ${expression}"      // String interpolation
+"value: {expression}"       // String interpolation
 "multi
 line
 string"
@@ -77,10 +74,13 @@ false
 | `\n` | Newline |
 | `\t` | Tab |
 | `\r` | Carriage return |
+| `\0` | Null character |
 | `\\` | Backslash |
 | `\"` | Double quote |
 | `\'` | Single quote |
-| `\$` | Dollar sign |
+| `\{` | Literal brace (in interpolated strings) |
+
+Note: Invalid escape sequences (e.g., `\z`) produce a parse error.
 
 ## Declarations