…arpdotdev#9409)

## Description

Renames a misspelled identifier (`delimeter` -> `delimiter`) across two
modules. Pure rename: 2 files, +9/-9 lines, no behavioral change.

**`app/src/env_vars/mod.rs`** - 6 changes:
- `pub fn export_variables(&self, delimeter: &str, ...)` -> `delimiter`
(parameter name)
- Internal call site
- Private `serialize_variables_internal(..., delimeter: &str, ...)`
parameter
- Three doc comments referencing the parameter

**`app/src/external_secrets/mod.rs`** - 3 changes:
- `static ref WARP_SECRET_DELIMETER` -> `WARP_SECRET_DELIMITER` (the
constant *identifier*)
- Two usages of the constant

### What is intentionally preserved

The **string literal value** `"/warp-secret-delimeter/"` on line 22 is
**kept as-is**. It is the runtime separator embedded in the `lpass
--format=%an{}%ai` command and split back out of lpass's output
(`line.split(*WARP_SECRET_DELIMITER)`). Changing the value would mean
output emitted with one delimiter is parsed with another, breaking
LastPass secret enumeration. Only the Rust identifier name is corrected;
the on-the-wire token is unchanged.

### Caller analysis

All three external call sites of `export_variables` (in
`drive/index.rs`, `drive/export.rs`, `terminal/input.rs`) use positional
arguments. Rust does not have named arguments, so the parameter rename
is invisible to callers and breaks nothing.

### Related

The comment `// Used as a delimeter to separate metadata` on line 20 of
`external_secrets/mod.rs` is deliberately left for PR warpdotdev#9404 (the round-3
typo bundle), which already includes that fix. Different lines, no
conflict.

## Testing

Pure identifier rename; no logic touched. The string-literal
preservation note above is the only correctness-relevant detail.

## Agent Mode

- [ ] Warp Agent Mode - This PR was created via Warp's AI Agent Mode

Co-authored-by: BennyWaitWhat <BennyWaitWhat@users.noreply.github.com>