Add project issues for lush (Lua + shell) features

Defines syntax decisions and implementation plan across 7 issues:
- backtick command execution returning {code, stdout, stderr}
- ${expr} interpolation in backticks
- $SIGIL env var read/write
- argv parsing, piping, and redirection (future)

issues/07-redirection.md

@@ -0,0 +1,28 @@
+# 07 — Implement I/O redirection for commands
+
+**Status:** open (post-core)
+**Blocked by:** #03
+
+## Syntax
+
+```lua
+`ls -l` > "output.txt"        -- redirect stdout to file
+`ls -l` >> "output.txt"       -- append stdout to file
+`cmd` 2> "err.txt"            -- redirect stderr to file
+`cmd` 2>&1                    -- merge stderr into stdout
+`cmd` < "input.txt"           -- redirect stdin from file
+```
+
+## Implementation
+
+- Before `execvp()` in the child process, use `dup2()` to redirect file descriptors
+- Parse redirection operators as part of the command syntax
+- Open target files with appropriate flags:
+  - `>` — `O_WRONLY | O_CREAT | O_TRUNC`
+  - `>>` — `O_WRONLY | O_CREAT | O_APPEND`
+  - `<` — `O_RDONLY`
+- `2>&1` — `dup2(stdout_fd, STDERR_FILENO)`
+
+## Challenge
+
+`>` and `>>` conflict with Lua's greater-than and right-shift operators. Like piping, these operators must only be valid in command context. The parser can disambiguate because the left-hand side is a command expression.