chore(terminal): remove committed terminal.so binaries, build from source

[theangelperalta]

Summary

Removes the three prebuilt terminal.so shared objects from version control and replaces them with a from-source build path. This is the follow-up to #2182 that finally addresses #1964 — "Open source software should, by definition, not be distributing binary files. Given the xz backdoor, these increase distrust."

#2182 added scripts/build-terminal.lisp and the make terminal-lib target but deliberately kept the binaries. This PR removes them and wires the build in.

Changes

• Remove binaries — git rm of extensions/terminal/lib/{linux/arm64,linux/x64,macosx/arm64}/terminal.so.
• Build on source installs — the ncurses, sdl2, sdl2-ncurses, webview and webview-ncurses targets now invoke terminal-lib best-effort via -$(MAKE) terminal-lib. A missing libvterm or C toolchain is non-fatal: lem-terminal/ffi.lisp already wraps cffi:use-foreign-library in ignore-errors and silently disables the terminal when the library is absent. Normal builds gain no hard libvterm dependency.
• gitignore extensions/terminal/lib/**/*.so so locally-built helpers are never re-committed.
• Convert the re-committing workflow — .github/workflows/build-terminal-shared-object.yml previously recompiled terminal.so and opened a PR to commit it back on every push to main, which would reintroduce exactly the binaries this removes. It's now a verify-only CI check that builds terminal.so from source on both Linux (apt libvterm) and macOS (brew libvterm) and fails if the build breaks — no commits, no artifacts.

Why this scope / risk

• lem-terminal is loaded best-effort, so removing the binaries cannot break make sdl2/ncurses/webview even where libvterm is unavailable.
• Release bundles (AppImage, macOS zip) do not currently ship or load terminal.so — ffi.lisp resolves it from the source-tree path via asdf:system-relative-pathname, so the committed binaries only ever served source/checkout installs. Bundling the terminal into release artifacts is a separate concern, left out of scope.

Test plan

• make terminal-lib on macOS arm64 (Homebrew libvterm) rebuilds extensions/terminal/lib/macosx/arm64/terminal.so (byte-identical size, 54232, to the removed binary).
• The rebuilt .so is gitignored (absent from git status).
• CI: make terminal-lib builds on Linux x64 (apt libvterm-dev) — verified by the new workflow.
• make sdl2 / ncurses / webview still build on a host without libvterm (terminal silently disabled).
• Open a *terminal* buffer from a fresh source build to confirm the freshly-built .so loads.

Refs #1964, #2060, #2182.

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=== Contract: contract ===

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📋 Contract Source: Repository

📊 Statistics:
  Files Changed:    3
  Lines Added:      0
  Lines Deleted:    0
  Total Changed:    0
  Delete Ratio:     0.00 (0%)

Status: PASSED ✅

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📋 Contract Configuration: contract (Source: Repository)

version: 2

trigger:
  paths:
    - "extensions/**"
    - "frontends/**/*.lisp"
    - "src/**"
    - "tests/**"
    - "contrib/**"
    - "**/*.asd"
  head_branches:
    exclude:
      - 'revert-*'

validation:
  limits:
    max_total_changed_lines: 400
    max_delete_ratio: 0.5
    max_files_changed: 10
    severity: warning

  ai:
    system_prompt: |
      You are a senior Common Lisp engineer reviewing code for Lem editor.
      Lem is a text editor with multiple frontends (ncurses, SDL2, webview).
      Focus on maintainability, consistency with existing code, and Lem-specific conventions.
    rules:
      # === File Structure ===
      - name: defpackage_rule
        prompt: |
          First form must be `defpackage` or `uiop:define-package`.
          Package name should match filename (e.g., `foo.lisp` → `:lem-ext/foo` or `:lem-foo`).
          Extensions must use `lem-` prefix (e.g., `:lem-python-mode`).

      - name: file_structure_rule
        prompt: |
          File organization (top to bottom):
          1. defpackage
          2. defvar/defparameter declarations
          3. Key bindings (define-key, define-keys)
          4. Class/struct definitions
          5. Functions and commands

      # === Style ===
      - name: loop_keywords_rule
        prompt: |
          Loop keywords must use colons: `(loop :for x :in list :do ...)`
          NOT: `(loop for x in list do ...)`

      - name: naming_conventions_rule
        prompt: |
          Naming conventions:
          - Functions/variables: kebab-case (e.g., `find-buffer`)
          - Special variables: *earmuffs* (e.g., `*global-keymap*`)
          - Constants: +plus-signs+ (e.g., `+default-tab-size+`)
          - Predicates: -p suffix for functions (e.g., `buffer-modified-p`)
          - Do NOT use -p suffix for user-configurable variables

      # === Documentation ===
      - name: docstring_rule
        prompt: |
          Required docstrings for:
          - Exported functions, methods, classes
          - `define-command` (explain what the command does)
          - Generic functions (`:documentation` option)
          Important functions should explain "why", not just "what".
        severity: warning

      # === Lem-Specific ===
      - name: internal_symbol_rule
        prompt: |
          Use exported symbols from `lem` or `lem-core` package.
          Avoid `lem::internal-symbol` access.
          If internal access is necessary, document why.

      - name: error_handling_rule
        prompt: |
          - `error`: Internal/programming errors
          - `editor-error`: User-facing errors (displayed in echo area)
          Always use `editor-error` for messages shown to users.

      - name: frontend_interface_rule
        prompt: |
          Frontend-specific code must use `lem-if:*` protocol.
          Do not call frontend implementation directly from core.
        severity: warning

      # === Functional Style ===
      - name: functional_style_rule
        prompt: |
          Prefer explicit function arguments over dynamic variables.
          Avoid using `defvar` for state passed between functions.
          Exception: Well-documented cases like `*current-buffer*`.

      - name: dynamic_symbol_call_rule
        prompt: |
          Avoid `uiop:symbol-call`. Rethink architecture instead.
          If unavoidable, document the reason.

      # === Libraries ===
      - name: alexandria_usage_rule
        prompt: |
          Alexandria utilities allowed: `if-let`, `when-let`, `with-gensyms`, etc.
          Avoid: `alexandria:curry` (use explicit lambdas)
          Avoid: `alexandria-2:*` functions not yet used in codebase

      # === Macros ===
      - name: macro_style_rule
        prompt: |
          Keep macros small. For complex logic, use `call-with-*` pattern:
          ```lisp
          (defmacro with-foo (() &body body)
            `(call-with-foo (lambda () ,@body)))
          ```
          Prefer `list` over backquote outside macros.

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