feat(security): security hardening, proxy support, and GL045 HTTP include warning

Security fixes:
- Path traversal guard in include: local: — paths with ../ that escape
  the repo root are rejected instead of reading arbitrary host files
- HTTP timeout (30 s) on all fetcher requests to prevent indefinite hangs
- Response size cap (10 MiB) via io.LimitReader to prevent memory exhaustion
- Cache directory and file permissions tightened to 0700/0600
- LSP Content-Length cap (64 MiB) to guard against DoS from a malicious client

New feature:
- --proxy flag on check, graph, and lsp subcommands; also proxy: key in
  .glint.yml; overrides system HTTP_PROXY / HTTPS_PROXY env vars when set;
  cmdGraph and cmdLSP now also load .glint.yml for proxy/token/url fallbacks

New lint rule:
- GL045 (Warning): include: remote: using plain http:// instead of https://

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ROADMAP.md

@@ -106,6 +106,18 @@ The SVG renderer and terminal tree cover the basic layout. These would bring it
 
 - [x] **`.glint.yml` config file** — shipped v0.2.19; `ignore:`, `severity:`, `stages:`, `token:`, `url:`, `cache_dir:`; searched from the pipeline directory up to the git root
 - [x] **Inline suppression comments** — shipped v0.2.19; `# glint: ignore GL007` before a job definition; comma/space-separated rules; `# glint: ignore all` wildcard
+- [x] **Proxy support** — shipped v0.2.31; `--proxy` flag on `check`, `graph`, and `lsp` subcommands; also configurable via `proxy:` in `.glint.yml`; overrides `HTTP_PROXY` / `HTTPS_PROXY` env vars when set
+
+---
+
+## Security & hardening
+
+- [x] **Path traversal guard for local includes** — shipped v0.2.31; `include: local:` paths containing `../../` or similar sequences are rejected instead of reading files outside the repository root
+- [x] **HTTP timeout on remote fetches** — shipped v0.2.31; all HTTP calls via the fetcher use a 30-second timeout to prevent indefinite hangs on slow or unresponsive servers
+- [x] **Unbounded response size cap** — shipped v0.2.31; remote include and GitLab API responses are capped at 10 MiB; responses exceeding the limit are rejected to prevent memory exhaustion
+- [x] **Cache file permissions** — shipped v0.2.31; cache directories are created with mode `0700` and cache files with mode `0600`; previously used world-readable `0755`/`0644`
+- [x] **GL045: HTTP remote include warning** — shipped v0.2.31; warns when `include: remote:` uses a plain `http://` URL; CI templates fetched unencrypted are at risk of tampering
+- [x] **LSP Content-Length DoS cap** — shipped v0.2.31; `glint lsp` rejects messages with `Content-Length` exceeding 64 MiB to prevent memory exhaustion from a malicious client
 
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