chore(idris2): add SPDX headers to idris2/src/*.idr (#134) (#88)

## Summary

Adds the estate-standard 3-line SPDX header (PMPL-1.0-or-later + your
Open.ac.uk copyright) to all 14 Idris2 source files under
\`idris2/src/\`, which were the last \`.idr\` files in the repo without
one.

## Why

\`src/formal/Ephapax/Formal/*.idr\` etc. already use this exact header;
\`idris2/src/*.idr\` were the sole gap. Standards #134 listed this as an
outstanding SPDX-coverage item.

## What

- 14 files touched, 42 insertions, 0 deletions, 0 modifications to
existing lines.
- Header is byte-identical to the existing template (RegionLinear.idr,
Qualifier.idr).
- Trailing newlines preserved.
- Idris2 ignores \`--\` comments before \`module …\`, so the build is
unchanged.

## Test plan

- [x] All 14 files now match the canonical SPDX template
- [x] No existing line modified, no trailing newlines stripped
- [x] Baseline rot in \`ephapax-parse-tests.ipkg\` (\`testLexPositions\`
/ \`parseWithBuf\` undefined) verified pre-existing on \`origin/main\`
and explicitly out of scope
- [ ] Repo CI (license-check + dogfood-gate) goes green

Refs hyperpolymath/standards#124 #134

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

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: hyperpolymath

idris2/src/Ephapax/Affine/Emit.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Affine.Emit
 
 import Ephapax.IR.Decode

idris2/src/Ephapax/Affine/Typecheck.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Affine.Typecheck
 
 import Data.List

idris2/src/Ephapax/IR/AST.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.IR.AST
 
 %default total

idris2/src/Ephapax/IR/Decode.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.IR.Decode
 
 import Data.List

idris2/src/Ephapax/IR/SExpr.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.IR.SExpr
 
 import Data.List

idris2/src/Ephapax/Parse/Lexer.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Parse.Lexer
 
 import Data.List

idris2/src/Ephapax/Parse/Parser.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Parse.Parser
 
 import Data.List

idris2/src/Ephapax/Parse/Stream.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Parse.Stream
 
 import Ephapax.Parse.Lexer

idris2/src/Ephapax/Parse/TestMain.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Parse.TestMain
 
 import Ephapax.Parse.Tests

idris2/src/Ephapax/Parse/Tests.idr

@@ -1,3 +1,6 @@
+-- SPDX-License-Identifier: PMPL-1.0-or-later
+-- Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+--
 module Ephapax.Parse.Tests
 
 import Data.List