docs: add comprehensive Programs concept page

- Create programs.md with detailed coverage of:
  - Program structure and components
  - Target types (individual vs group)
  - Program managers and their roles
  - Program lifecycle (active/ended)
  - Membership states and transitions
  - Key operations (import, verify, enroll, deduplicate)
  - Entitlements and their states
  - Common program types (UCT, CCT, emergency, agricultural)
  - Data model overview with mermaid ER diagram
  - Troubleshooting FAQ
- Restore cel_lexer.py extension (was accidentally deleted)
- Add _ext directory to sys.path in conf.py for custom extensions

Content based on V2 spp_programs module code for accuracy.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: Jeremi

docs/_ext/cel_lexer.py

@@ -0,0 +1,161 @@
+"""
+CEL (Common Expression Language) Pygments Lexer for OpenSPP
+
+This lexer provides syntax highlighting for CEL expressions used in OpenSPP
+eligibility rules, entitlement formulas, and other configuration expressions.
+
+Based on the CodeMirror implementation in spp_cel_widget.
+"""
+
+from pygments.lexer import RegexLexer, bygroups, words
+from pygments.token import (
+    Comment,
+    Keyword,
+    Name,
+    Number,
+    Operator,
+    Punctuation,
+    String,
+    Text,
+    Whitespace,
+)
+
+__all__ = ["CelLexer"]
+
+
+class CelLexer(RegexLexer):
+    """
+    Lexer for CEL (Common Expression Language) expressions.
+
+    CEL is used in OpenSPP for eligibility rules and entitlement formulas.
+    """
+
+    name = "CEL"
+    aliases = ["cel"]
+    filenames = ["*.cel"]
+    mimetypes = ["text/x-cel"]
+
+    # CEL keywords
+    keywords = (
+        "and",
+        "or",
+        "not",
+        "in",
+    )
+
+    # Boolean and null literals
+    constants = (
+        "true",
+        "false",
+        "null",
+    )
+
+    # CEL built-in functions from OpenSPP
+    builtins = (
+        "age_years",
+        "today",
+        "now",
+        "days_ago",
+        "months_ago",
+        "years_ago",
+        "between",
+        "exists",
+        "count",
+        "head",
+        "has_role",
+        "contains",
+        "startswith",
+        "endswith",
+        "metric",
+        "program",
+        "has_tag",
+        "date",
+        "days_since",
+        "hours_since",
+        "is_business_day",
+        "min",
+        "max",
+        "sum",
+        "avg",
+        "abs",
+        "size",
+        "matches",
+        "filter",
+        "map",
+        "all",
+        "exists_one",
+        "type",
+        "string",
+        "int",
+        "uint",
+        "double",
+        "bool",
+        "duration",
+        "timestamp",
+    )
+
+    tokens = {
+        "root": [
+            # Whitespace
+            (r"\s+", Whitespace),
+            # Comments (// style)
+            (r"//.*$", Comment.Single),
+            # Strings (double-quoted)
+            (r'"', String.Double, "string-double"),
+            # Strings (single-quoted)
+            (r"'", String.Single, "string-single"),
+            # Numbers (integers and floats)
+            (r"-?\d+\.\d+", Number.Float),
+            (r"-?\d+", Number.Integer),
+            # Boolean and null constants
+            (words(constants, suffix=r"\b"), Keyword.Constant),
+            # Keywords
+            (words(keywords, suffix=r"\b"), Keyword),
+            # Built-in functions (followed by parenthesis)
+            (
+                r"(" + "|".join(builtins) + r")(\s*)(\()",
+                bygroups(Name.Builtin, Whitespace, Punctuation),
+            ),
+            # Function calls (identifier followed by parenthesis)
+            (r"([a-zA-Z_][a-zA-Z0-9_]*)(\s*)(\()", bygroups(Name.Function, Whitespace, Punctuation)),
+            # Property access (after dot)
+            (r"(\.)([a-zA-Z_][a-zA-Z0-9_]*)", bygroups(Punctuation, Name.Attribute)),
+            # Comparison operators (must be before single char operators)
+            (r"==|!=|>=|<=|&&|\|\|", Operator),
+            # Single char operators
+            (r"[<>=!+\-*/%]", Operator),
+            # Punctuation
+            (r"[.,\(\)\[\]\{\}:]", Punctuation),
+            # Identifiers (variables)
+            (r"[a-zA-Z_][a-zA-Z0-9_]*", Name.Variable),
+            # Catch-all for other characters
+            (r".", Text),
+        ],
+        "string-double": [
+            (r'\\[\\"]', String.Escape),
+            (r'[^"\\]+', String.Double),
+            (r'"', String.Double, "#pop"),
+        ],
+        "string-single": [
+            (r"\\[\\']", String.Escape),
+            (r"[^'\\]+", String.Single),
+            (r"'", String.Single, "#pop"),
+        ],
+    }
+
+
+def setup(app):
+    """
+    Sphinx extension setup function.
+
+    Registers the CEL lexer with Pygments so it can be used in code blocks.
+    """
+    from sphinx.highlighting import lexers
+
+    lexers["cel"] = CelLexer(startinline=True)
+
+    return {
+        "version": "1.0",
+        "parallel_read_safe": True,
+        "parallel_write_safe": True,
+    }

docs/conf.py

@@ -20,9 +20,8 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
-# import os
-# import sys
-# sys.path.insert(0, os.path.abspath("."))
+# Add _ext directory to sys.path for custom extensions (e.g., cel_lexer)
+sys.path.insert(0, os.path.abspath("_ext"))