docs: add missing feature examples

New examples:
- interactive.i.claude.md: Interactive mode via .i. filename
- command-inline.claude.md: Shell command inlines (!`cmd`)
- line-range.claude.md: Line range imports (@file:10-50)
- symbol-extract.claude.md: TypeScript symbol extraction (@file#Symbol)
- subcommand.codex.md: _subcommand for codex exec

Author: johnlindquist

examples/command-inline.claude.md

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+---
+# Command inlines - embed shell command output in prompts
+# Usage: md command-inline.claude.md
+model: sonnet
+print: true
+---
+
+Based on the current git status:
+!`git status --short`
+
+And recent commits:
+!`git log --oneline -5`
+
+What should I work on next?

examples/interactive.i.claude.md

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+---
+# Interactive mode - the .i. in filename enables interactive session
+# Usage: md interactive.i.claude.md
+# This runs: claude "..." (no --print flag, stays in session)
+model: sonnet
+---
+
+Let's have a conversation about this codebase.
+
+@./src/index.ts

examples/line-range.claude.md

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+---
+# Line range imports - extract specific lines from a file
+# Usage: md line-range.claude.md
+model: sonnet
+print: true
+---
+
+Explain what this section of the CLI runner does:
+
+@./src/cli-runner.ts:136-160

examples/subcommand.codex.md

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+---
+# Subcommand - prepend subcommands to CLI args
+# Usage: md subcommand.codex.md
+# This runs: codex exec --full-auto "..."
+_subcommand: exec
+full-auto: true
+---
+
+Analyze this codebase and suggest improvements.

examples/symbol-extract.claude.md

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+---
+# Symbol extraction - extract specific TypeScript symbols
+# Usage: md symbol-extract.claude.md
+model: sonnet
+print: true
+---
+
+Explain this interface and suggest improvements:
+
+@./src/types.ts#AgentFrontmatter